text: //===--- ItaniumMangle.cpp - Itanium C++ Name Mangling ----------*- C++ -*-===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  // Implements C++ name mangling according to the Itanium C++ ABI,
  // which is used in GCC 3.2 and newer (and many compilers that are
  // ABI-compatible with GCC):
  //
  //   http://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/AST/Mangle.h"
  #include "clang/AST/ASTContext.h"
  #include "clang/AST/Attr.h"
  #include "clang/AST/Decl.h"
  #include "clang/AST/DeclCXX.h"
  #include "clang/AST/DeclObjC.h"
  #include "clang/AST/DeclOpenMP.h"
  #include "clang/AST/DeclTemplate.h"
  #include "clang/AST/Expr.h"
  #include "clang/AST/ExprConcepts.h"
  #include "clang/AST/ExprCXX.h"
  #include "clang/AST/ExprObjC.h"
  #include "clang/AST/TypeLoc.h"
  #include "clang/Basic/ABI.h"
  #include "clang/Basic/Module.h"
  #include "clang/Basic/SourceManager.h"
  #include "clang/Basic/TargetInfo.h"
  #include "llvm/ADT/StringExtras.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/raw_ostream.h"
  
  using namespace clang;
  
  namespace {
  
  /// Retrieve the declaration context that should be used when mangling the given
  /// declaration.
  static const DeclContext *getEffectiveDeclContext(const Decl *D) {
    // The ABI assumes that lambda closure types that occur within
    // default arguments live in the context of the function. However, due to
    // the way in which Clang parses and creates function declarations, this is
    // not the case: the lambda closure type ends up living in the context
    // where the function itself resides, because the function declaration itself
    // had not yet been created. Fix the context here.
    if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D)) {
      if (RD->isLambda())
        if (ParmVarDecl *ContextParam
              = dyn_cast_or_null<ParmVarDecl>(RD->getLambdaContextDecl()))
          return ContextParam->getDeclContext();
    }
  
    // Perform the same check for block literals.
    if (const BlockDecl *BD = dyn_cast<BlockDecl>(D)) {
      if (ParmVarDecl *ContextParam
            = dyn_cast_or_null<ParmVarDecl>(BD->getBlockManglingContextDecl()))
        return ContextParam->getDeclContext();
    }
  
    const DeclContext *DC = D->getDeclContext();
    if (isa<CapturedDecl>(DC) || isa<OMPDeclareReductionDecl>(DC) ||
        isa<OMPDeclareMapperDecl>(DC)) {
      return getEffectiveDeclContext(cast<Decl>(DC));
    }
  
    if (const auto *VD = dyn_cast<VarDecl>(D))
      if (VD->isExternC())
        return VD->getASTContext().getTranslationUnitDecl();
  
    if (const auto *FD = dyn_cast<FunctionDecl>(D))
      if (FD->isExternC())
        return FD->getASTContext().getTranslationUnitDecl();
  
    return DC->getRedeclContext();
  }
  
  static const DeclContext *getEffectiveParentContext(const DeclContext *DC) {
    return getEffectiveDeclContext(cast<Decl>(DC));
  }
  
  static bool isLocalContainerContext(const DeclContext *DC) {
    return isa<FunctionDecl>(DC) || isa<ObjCMethodDecl>(DC) || isa<BlockDecl>(DC);
  }
  
  static const RecordDecl *GetLocalClassDecl(const Decl *D) {
    const DeclContext *DC = getEffectiveDeclContext(D);
    while (!DC->isNamespace() && !DC->isTranslationUnit()) {
      if (isLocalContainerContext(DC))
        return dyn_cast<RecordDecl>(D);
      D = cast<Decl>(DC);
      DC = getEffectiveDeclContext(D);
    }
    return nullptr;
  }
  
  static const FunctionDecl *getStructor(const FunctionDecl *fn) {
    if (const FunctionTemplateDecl *ftd = fn->getPrimaryTemplate())
      return ftd->getTemplatedDecl();
  
    return fn;
  }
  
  static const NamedDecl *getStructor(const NamedDecl *decl) {
    const FunctionDecl *fn = dyn_cast_or_null<FunctionDecl>(decl);
    return (fn ? getStructor(fn) : decl);
  }
  
  static bool isLambda(const NamedDecl *ND) {
    const CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(ND);
    if (!Record)
      return false;
  
    return Record->isLambda();
  }
  
  static const unsigned UnknownArity = ~0U;
  
  class ItaniumMangleContextImpl : public ItaniumMangleContext {
    typedef std::pair<const DeclContext*, IdentifierInfo*> DiscriminatorKeyTy;
    llvm::DenseMap<DiscriminatorKeyTy, unsigned> Discriminator;
    llvm::DenseMap<const NamedDecl*, unsigned> Uniquifier;
  
  public:
    explicit ItaniumMangleContextImpl(ASTContext &Context,
                                      DiagnosticsEngine &Diags)
        : ItaniumMangleContext(Context, Diags) {}
  
    /// @name Mangler Entry Points
    /// @{
  
    bool shouldMangleCXXName(const NamedDecl *D) override;
    bool shouldMangleStringLiteral(const StringLiteral *) override {
      return false;
    }
    void mangleCXXName(GlobalDecl GD, raw_ostream &) override;
    void mangleThunk(const CXXMethodDecl *MD, const ThunkInfo &Thunk,
                     raw_ostream &) override;
    void mangleCXXDtorThunk(const CXXDestructorDecl *DD, CXXDtorType Type,
                            const ThisAdjustment &ThisAdjustment,
                            raw_ostream &) override;
    void mangleReferenceTemporary(const VarDecl *D, unsigned ManglingNumber,
                                  raw_ostream &) override;
    void mangleCXXVTable(const CXXRecordDecl *RD, raw_ostream &) override;
    void mangleCXXVTT(const CXXRecordDecl *RD, raw_ostream &) override;
    void mangleCXXCtorVTable(const CXXRecordDecl *RD, int64_t Offset,
                             const CXXRecordDecl *Type, raw_ostream &) override;
    void mangleCXXRTTI(QualType T, raw_ostream &) override;
    void mangleCXXRTTIName(QualType T, raw_ostream &) override;
    void mangleTypeName(QualType T, raw_ostream &) override;
  
    void mangleCXXCtorComdat(const CXXConstructorDecl *D, raw_ostream &) override;
    void mangleCXXDtorComdat(const CXXDestructorDecl *D, raw_ostream &) override;
    void mangleStaticGuardVariable(const VarDecl *D, raw_ostream &) override;
    void mangleDynamicInitializer(const VarDecl *D, raw_ostream &Out) override;
    void mangleDynamicAtExitDestructor(const VarDecl *D,
                                       raw_ostream &Out) override;
    void mangleDynamicStermFinalizer(const VarDecl *D, raw_ostream &Out) override;
    void mangleSEHFilterExpression(const NamedDecl *EnclosingDecl,
                                   raw_ostream &Out) override;
    void mangleSEHFinallyBlock(const NamedDecl *EnclosingDecl,
                               raw_ostream &Out) override;
    void mangleItaniumThreadLocalInit(const VarDecl *D, raw_ostream &) override;
    void mangleItaniumThreadLocalWrapper(const VarDecl *D,
                                         raw_ostream &) override;
  
    void mangleStringLiteral(const StringLiteral *, raw_ostream &) override;
  
    void mangleLambdaSig(const CXXRecordDecl *Lambda, raw_ostream &) override;
  
    bool getNextDiscriminator(const NamedDecl *ND, unsigned &disc) {
      // Lambda closure types are already numbered.
      if (isLambda(ND))
        return false;
  
      // Anonymous tags are already numbered.
      if (const TagDecl *Tag = dyn_cast<TagDecl>(ND)) {
        if (Tag->getName().empty() && !Tag->getTypedefNameForAnonDecl())
          return false;
      }
  
      // Use the canonical number for externally visible decls.
      if (ND->isExternallyVisible()) {
        unsigned discriminator = getASTContext().getManglingNumber(ND);
        if (discriminator == 1)
          return false;
        disc = discriminator - 2;
        return true;
      }
  
      // Make up a reasonable number for internal decls.
      unsigned &discriminator = Uniquifier[ND];
      if (!discriminator) {
        const DeclContext *DC = getEffectiveDeclContext(ND);
        discriminator = ++Discriminator[std::make_pair(DC, ND->getIdentifier())];
      }
      if (discriminator == 1)
        return false;
      disc = discriminator-2;
      return true;
    }
    /// @}
  };
  
  /// Manage the mangling of a single name.
  class CXXNameMangler {
    ItaniumMangleContextImpl &Context;
    raw_ostream &Out;
    bool NullOut = false;
    /// In the "DisableDerivedAbiTags" mode derived ABI tags are not calculated.
    /// This mode is used when mangler creates another mangler recursively to
    /// calculate ABI tags for the function return value or the variable type.
    /// Also it is required to avoid infinite recursion in some cases.
    bool DisableDerivedAbiTags = false;
  
    /// The "structor" is the top-level declaration being mangled, if
    /// that's not a template specialization; otherwise it's the pattern
    /// for that specialization.
    const NamedDecl *Structor;
    unsigned StructorType;
  
    /// The next substitution sequence number.
    unsigned SeqID;
  
    class FunctionTypeDepthState {
      unsigned Bits;
  
      enum { InResultTypeMask = 1 };
  
    public:
      FunctionTypeDepthState() : Bits(0) {}
  
      /// The number of function types we're inside.
      unsigned getDepth() const {
        return Bits >> 1;
      }
  
      /// True if we're in the return type of the innermost function type.
      bool isInResultType() const {
        return Bits & InResultTypeMask;
      }
  
      FunctionTypeDepthState push() {
        FunctionTypeDepthState tmp = *this;
        Bits = (Bits & ~InResultTypeMask) + 2;
        return tmp;
      }
  
      void enterResultType() {
        Bits |= InResultTypeMask;
      }
  
      void leaveResultType() {
        Bits &= ~InResultTypeMask;
      }
  
      void pop(FunctionTypeDepthState saved) {
        assert(getDepth() == saved.getDepth() + 1);
        Bits = saved.Bits;
      }
  
    } FunctionTypeDepth;
  
    // abi_tag is a gcc attribute, taking one or more strings called "tags".
    // The goal is to annotate against which version of a library an object was
    // built and to be able to provide backwards compatibility ("dual abi").
    // For more information see docs/ItaniumMangleAbiTags.rst.
    typedef SmallVector<StringRef, 4> AbiTagList;
  
    // State to gather all implicit and explicit tags used in a mangled name.
    // Must always have an instance of this while emitting any name to keep
    // track.
    class AbiTagState final {
    public:
      explicit AbiTagState(AbiTagState *&Head) : LinkHead(Head) {
        Parent = LinkHead;
        LinkHead = this;
      }
  
      // No copy, no move.
      AbiTagState(const AbiTagState &) = delete;
      AbiTagState &operator=(const AbiTagState &) = delete;
  
      ~AbiTagState() { pop(); }
  
      void write(raw_ostream &Out, const NamedDecl *ND,
                 const AbiTagList *AdditionalAbiTags) {
        ND = cast<NamedDecl>(ND->getCanonicalDecl());
        if (!isa<FunctionDecl>(ND) && !isa<VarDecl>(ND)) {
          assert(
              !AdditionalAbiTags &&
              "only function and variables need a list of additional abi tags");
          if (const auto *NS = dyn_cast<NamespaceDecl>(ND)) {
            if (const auto *AbiTag = NS->getAttr<AbiTagAttr>()) {
              UsedAbiTags.insert(UsedAbiTags.end(), AbiTag->tags().begin(),
                                 AbiTag->tags().end());
            }
            // Don't emit abi tags for namespaces.
            return;
          }
        }
  
        AbiTagList TagList;
        if (const auto *AbiTag = ND->getAttr<AbiTagAttr>()) {
          UsedAbiTags.insert(UsedAbiTags.end(), AbiTag->tags().begin(),
                             AbiTag->tags().end());
          TagList.insert(TagList.end(), AbiTag->tags().begin(),
                         AbiTag->tags().end());
        }
  
        if (AdditionalAbiTags) {
          UsedAbiTags.insert(UsedAbiTags.end(), AdditionalAbiTags->begin(),
                             AdditionalAbiTags->end());
          TagList.insert(TagList.end(), AdditionalAbiTags->begin(),
                         AdditionalAbiTags->end());
        }
  
        llvm::sort(TagList);
        TagList.erase(std::unique(TagList.begin(), TagList.end()), TagList.end());
  
        writeSortedUniqueAbiTags(Out, TagList);
      }
  
      const AbiTagList &getUsedAbiTags() const { return UsedAbiTags; }
      void setUsedAbiTags(const AbiTagList &AbiTags) {
        UsedAbiTags = AbiTags;
      }
  
      const AbiTagList &getEmittedAbiTags() const {
        return EmittedAbiTags;
      }
  
      const AbiTagList &getSortedUniqueUsedAbiTags() {
        llvm::sort(UsedAbiTags);
        UsedAbiTags.erase(std::unique(UsedAbiTags.begin(), UsedAbiTags.end()),
                          UsedAbiTags.end());
        return UsedAbiTags;
      }
  
    private:
      //! All abi tags used implicitly or explicitly.
      AbiTagList UsedAbiTags;
      //! All explicit abi tags (i.e. not from namespace).
      AbiTagList EmittedAbiTags;
  
      AbiTagState *&LinkHead;
      AbiTagState *Parent = nullptr;
  
      void pop() {
        assert(LinkHead == this &&
               "abi tag link head must point to us on destruction");
        if (Parent) {
          Parent->UsedAbiTags.insert(Parent->UsedAbiTags.end(),
                                     UsedAbiTags.begin(), UsedAbiTags.end());
          Parent->EmittedAbiTags.insert(Parent->EmittedAbiTags.end(),
                                        EmittedAbiTags.begin(),
                                        EmittedAbiTags.end());
        }
        LinkHead = Parent;
      }
  
      void writeSortedUniqueAbiTags(raw_ostream &Out, const AbiTagList &AbiTags) {
        for (const auto &Tag : AbiTags) {
          EmittedAbiTags.push_back(Tag);
          Out << "B";
          Out << Tag.size();
          Out << Tag;
        }
      }
    };
  
    AbiTagState *AbiTags = nullptr;
    AbiTagState AbiTagsRoot;
  
    llvm::DenseMap<uintptr_t, unsigned> Substitutions;
    llvm::DenseMap<StringRef, unsigned> ModuleSubstitutions;
  
    ASTContext &getASTContext() const { return Context.getASTContext(); }
  
  public:
    CXXNameMangler(ItaniumMangleContextImpl &C, raw_ostream &Out_,
                   const NamedDecl *D = nullptr, bool NullOut_ = false)
      : Context(C), Out(Out_), NullOut(NullOut_),  Structor(getStructor(D)),
        StructorType(0), SeqID(0), AbiTagsRoot(AbiTags) {
      // These can't be mangled without a ctor type or dtor type.
      assert(!D || (!isa<CXXDestructorDecl>(D) &&
                    !isa<CXXConstructorDecl>(D)));
    }
    CXXNameMangler(ItaniumMangleContextImpl &C, raw_ostream &Out_,
                   const CXXConstructorDecl *D, CXXCtorType Type)
      : Context(C), Out(Out_), Structor(getStructor(D)), StructorType(Type),
        SeqID(0), AbiTagsRoot(AbiTags) { }
    CXXNameMangler(ItaniumMangleContextImpl &C, raw_ostream &Out_,
                   const CXXDestructorDecl *D, CXXDtorType Type)
      : Context(C), Out(Out_), Structor(getStructor(D)), StructorType(Type),
        SeqID(0), AbiTagsRoot(AbiTags) { }
  
    CXXNameMangler(CXXNameMangler &Outer, raw_ostream &Out_)
        : Context(Outer.Context), Out(Out_), NullOut(false),
          Structor(Outer.Structor), StructorType(Outer.StructorType),
          SeqID(Outer.SeqID), FunctionTypeDepth(Outer.FunctionTypeDepth),
          AbiTagsRoot(AbiTags), Substitutions(Outer.Substitutions) {}
  
    CXXNameMangler(CXXNameMangler &Outer, llvm::raw_null_ostream &Out_)
        : Context(Outer.Context), Out(Out_), NullOut(true),
          Structor(Outer.Structor), StructorType(Outer.StructorType),
          SeqID(Outer.SeqID), FunctionTypeDepth(Outer.FunctionTypeDepth),
          AbiTagsRoot(AbiTags), Substitutions(Outer.Substitutions) {}
  
    raw_ostream &getStream() { return Out; }
  
    void disableDerivedAbiTags() { DisableDerivedAbiTags = true; }
    static bool shouldHaveAbiTags(ItaniumMangleContextImpl &C, const VarDecl *VD);
  
    void mangle(GlobalDecl GD);
    void mangleCallOffset(int64_t NonVirtual, int64_t Virtual);
    void mangleNumber(const llvm::APSInt &I);
    void mangleNumber(int64_t Number);
    void mangleFloat(const llvm::APFloat &F);
    void mangleFunctionEncoding(GlobalDecl GD);
    void mangleSeqID(unsigned SeqID);
    void mangleName(GlobalDecl GD);
    void mangleType(QualType T);
    void mangleNameOrStandardSubstitution(const NamedDecl *ND);
    void mangleLambdaSig(const CXXRecordDecl *Lambda);
  
  private:
  
    bool mangleSubstitution(const NamedDecl *ND);
    bool mangleSubstitution(QualType T);
    bool mangleSubstitution(TemplateName Template);
    bool mangleSubstitution(uintptr_t Ptr);
  
    void mangleExistingSubstitution(TemplateName name);
  
    bool mangleStandardSubstitution(const NamedDecl *ND);
  
    void addSubstitution(const NamedDecl *ND) {
      ND = cast<NamedDecl>(ND->getCanonicalDecl());
  
      addSubstitution(reinterpret_cast<uintptr_t>(ND));
    }
    void addSubstitution(QualType T);
    void addSubstitution(TemplateName Template);
    void addSubstitution(uintptr_t Ptr);
    // Destructive copy substitutions from other mangler.
    void extendSubstitutions(CXXNameMangler* Other);
  
    void mangleUnresolvedPrefix(NestedNameSpecifier *qualifier,
                                bool recursive = false);
    void mangleUnresolvedName(NestedNameSpecifier *qualifier,
                              DeclarationName name,
                              const TemplateArgumentLoc *TemplateArgs,
                              unsigned NumTemplateArgs,
                              unsigned KnownArity = UnknownArity);
  
    void mangleFunctionEncodingBareType(const FunctionDecl *FD);
  
    void mangleNameWithAbiTags(GlobalDecl GD,
                               const AbiTagList *AdditionalAbiTags);
    void mangleModuleName(const Module *M);
    void mangleModuleNamePrefix(StringRef Name);
    void mangleTemplateName(const TemplateDecl *TD,
                            const TemplateArgument *TemplateArgs,
                            unsigned NumTemplateArgs);
    void mangleUnqualifiedName(GlobalDecl GD,
                               const AbiTagList *AdditionalAbiTags) {
      mangleUnqualifiedName(GD, cast<NamedDecl>(GD.getDecl())->getDeclName(), UnknownArity,
                            AdditionalAbiTags);
    }
    void mangleUnqualifiedName(GlobalDecl GD, DeclarationName Name,
                               unsigned KnownArity,
                               const AbiTagList *AdditionalAbiTags);
    void mangleUnscopedName(GlobalDecl GD,
                            const AbiTagList *AdditionalAbiTags);
    void mangleUnscopedTemplateName(GlobalDecl GD,
                                    const AbiTagList *AdditionalAbiTags);
    void mangleUnscopedTemplateName(TemplateName,
                                    const AbiTagList *AdditionalAbiTags);
    void mangleSourceName(const IdentifierInfo *II);
    void mangleRegCallName(const IdentifierInfo *II);
    void mangleDeviceStubName(const IdentifierInfo *II);
    void mangleSourceNameWithAbiTags(
        const NamedDecl *ND, const AbiTagList *AdditionalAbiTags = nullptr);
    void mangleLocalName(GlobalDecl GD,
                         const AbiTagList *AdditionalAbiTags);
    void mangleBlockForPrefix(const BlockDecl *Block);
    void mangleUnqualifiedBlock(const BlockDecl *Block);
    void mangleTemplateParamDecl(const NamedDecl *Decl);
    void mangleLambda(const CXXRecordDecl *Lambda);
    void mangleNestedName(GlobalDecl GD, const DeclContext *DC,
                          const AbiTagList *AdditionalAbiTags,
                          bool NoFunction=false);
    void mangleNestedName(const TemplateDecl *TD,
                          const TemplateArgument *TemplateArgs,
                          unsigned NumTemplateArgs);
    void manglePrefix(NestedNameSpecifier *qualifier);
    void manglePrefix(const DeclContext *DC, bool NoFunction=false);
    void manglePrefix(QualType type);
    void mangleTemplatePrefix(GlobalDecl GD, bool NoFunction=false);
    void mangleTemplatePrefix(TemplateName Template);
    bool mangleUnresolvedTypeOrSimpleId(QualType DestroyedType,
                                        StringRef Prefix = "");
    void mangleOperatorName(DeclarationName Name, unsigned Arity);
    void mangleOperatorName(OverloadedOperatorKind OO, unsigned Arity);
    void mangleVendorQualifier(StringRef qualifier);
    void mangleQualifiers(Qualifiers Quals, const DependentAddressSpaceType *DAST = nullptr);
    void mangleRefQualifier(RefQualifierKind RefQualifier);
  
    void mangleObjCMethodName(const ObjCMethodDecl *MD);
  
    // Declare manglers for every type class.
  #define ABSTRACT_TYPE(CLASS, PARENT)
  #define NON_CANONICAL_TYPE(CLASS, PARENT)
  #define TYPE(CLASS, PARENT) void mangleType(const CLASS##Type *T);
  #include "clang/AST/TypeNodes.inc"
  
    void mangleType(const TagType*);
    void mangleType(TemplateName);
    static StringRef getCallingConvQualifierName(CallingConv CC);
    void mangleExtParameterInfo(FunctionProtoType::ExtParameterInfo info);
    void mangleExtFunctionInfo(const FunctionType *T);
    void mangleBareFunctionType(const FunctionProtoType *T, bool MangleReturnType,
                                const FunctionDecl *FD = nullptr);
    void mangleNeonVectorType(const VectorType *T);
    void mangleNeonVectorType(const DependentVectorType *T);
    void mangleAArch64NeonVectorType(const VectorType *T);
    void mangleAArch64NeonVectorType(const DependentVectorType *T);
    void mangleAArch64FixedSveVectorType(const VectorType *T);
    void mangleAArch64FixedSveVectorType(const DependentVectorType *T);
  
    void mangleIntegerLiteral(QualType T, const llvm::APSInt &Value);
    void mangleMemberExprBase(const Expr *base, bool isArrow);
    void mangleMemberExpr(const Expr *base, bool isArrow,
                          NestedNameSpecifier *qualifier,
                          NamedDecl *firstQualifierLookup,
                          DeclarationName name,
                          const TemplateArgumentLoc *TemplateArgs,
                          unsigned NumTemplateArgs,
                          unsigned knownArity);
    void mangleCastExpression(const Expr *E, StringRef CastEncoding);
    void mangleInitListElements(const InitListExpr *InitList);
    void mangleDeclRefExpr(const NamedDecl *D);
    void mangleExpression(const Expr *E, unsigned Arity = UnknownArity);
    void mangleCXXCtorType(CXXCtorType T, const CXXRecordDecl *InheritedFrom);
    void mangleCXXDtorType(CXXDtorType T);
  
    void mangleTemplateArgs(const TemplateArgumentLoc *TemplateArgs,
                            unsigned NumTemplateArgs);
    void mangleTemplateArgs(const TemplateArgument *TemplateArgs,
                            unsigned NumTemplateArgs);
    void mangleTemplateArgs(const TemplateArgumentList &AL);
    void mangleTemplateArg(TemplateArgument A);
  
    void mangleTemplateParameter(unsigned Depth, unsigned Index);
  
    void mangleFunctionParam(const ParmVarDecl *parm);
  
    void writeAbiTags(const NamedDecl *ND,
                      const AbiTagList *AdditionalAbiTags);
  
    // Returns sorted unique list of ABI tags.
    AbiTagList makeFunctionReturnTypeTags(const FunctionDecl *FD);
    // Returns sorted unique list of ABI tags.
    AbiTagList makeVariableTypeTags(const VarDecl *VD);
  };
  
  }
  
  bool ItaniumMangleContextImpl::shouldMangleCXXName(const NamedDecl *D) {
    const FunctionDecl *FD = dyn_cast<FunctionDecl>(D);
    if (FD) {
      LanguageLinkage L = FD->getLanguageLinkage();
      // Overloadable functions need mangling.
      if (FD->hasAttr<OverloadableAttr>())
        return true;
  
      // "main" is not mangled.
      if (FD->isMain())
        return false;
  
      // The Windows ABI expects that we would never mangle "typical"
      // user-defined entry points regardless of visibility or freestanding-ness.
      //
      // N.B. This is distinct from asking about "main".  "main" has a lot of
      // special rules associated with it in the standard while these
      // user-defined entry points are outside of the purview of the standard.
      // For example, there can be only one definition for "main" in a standards
      // compliant program; however nothing forbids the existence of wmain and
      // WinMain in the same translation unit.
      if (FD->isMSVCRTEntryPoint())
        return false;
  
      // C++ functions and those whose names are not a simple identifier need
      // mangling.
      if (!FD->getDeclName().isIdentifier() || L == CXXLanguageLinkage)
        return true;
  
      // C functions are not mangled.
      if (L == CLanguageLinkage)
        return false;
    }
  
    // Otherwise, no mangling is done outside C++ mode.
    if (!getASTContext().getLangOpts().CPlusPlus)
      return false;
  
    const VarDecl *VD = dyn_cast<VarDecl>(D);
    if (VD && !isa<DecompositionDecl>(D)) {
      // C variables are not mangled.
      if (VD->isExternC())
        return false;
  
      // Variables at global scope with non-internal linkage are not mangled
      const DeclContext *DC = getEffectiveDeclContext(D);
      // Check for extern variable declared locally.
      if (DC->isFunctionOrMethod() && D->hasLinkage())
        while (!DC->isNamespace() && !DC->isTranslationUnit())
          DC = getEffectiveParentContext(DC);
      if (DC->isTranslationUnit() && D->getFormalLinkage() != InternalLinkage &&
          !CXXNameMangler::shouldHaveAbiTags(*this, VD) &&
          !isa<VarTemplateSpecializationDecl>(D))
        return false;
    }
  
    return true;
  }
  
  void CXXNameMangler::writeAbiTags(const NamedDecl *ND,
                                    const AbiTagList *AdditionalAbiTags) {
    assert(AbiTags && "require AbiTagState");
    AbiTags->write(Out, ND, DisableDerivedAbiTags ? nullptr : AdditionalAbiTags);
  }
  
  void CXXNameMangler::mangleSourceNameWithAbiTags(
      const NamedDecl *ND, const AbiTagList *AdditionalAbiTags) {
    mangleSourceName(ND->getIdentifier());
    writeAbiTags(ND, AdditionalAbiTags);
  }
  
  void CXXNameMangler::mangle(GlobalDecl GD) {
    // <mangled-name> ::= _Z <encoding>
    //            ::= <data name>
    //            ::= <special-name>
    Out << "_Z";
    if (isa<FunctionDecl>(GD.getDecl()))
      mangleFunctionEncoding(GD);
    else if (const VarDecl *VD = dyn_cast<VarDecl>(GD.getDecl()))
      mangleName(VD);
    else if (const IndirectFieldDecl *IFD =
                 dyn_cast<IndirectFieldDecl>(GD.getDecl()))
      mangleName(IFD->getAnonField());
    else if (const FieldDecl *FD = dyn_cast<FieldDecl>(GD.getDecl()))
      mangleName(FD);
    else if (const MSGuidDecl *GuidD = dyn_cast<MSGuidDecl>(GD.getDecl()))
      mangleName(GuidD);
    else if (const BindingDecl *BD = dyn_cast<BindingDecl>(GD.getDecl()))
      mangleName(BD);
    else if (isa<TemplateParamObjectDecl>(GD.getDecl())) {
      DiagnosticsEngine &Diags = Context.getDiags();
      unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
        "cannot mangle template parameter objects yet");
      Diags.Report(SourceLocation(), DiagID);
    } else
      llvm_unreachable("unexpected kind of global decl");
  }
  
  void CXXNameMangler::mangleFunctionEncoding(GlobalDecl GD) {
    const FunctionDecl *FD = cast<FunctionDecl>(GD.getDecl());
    // <encoding> ::= <function name> <bare-function-type>
  
    // Don't mangle in the type if this isn't a decl we should typically mangle.
    if (!Context.shouldMangleDeclName(FD)) {
      mangleName(GD);
      return;
    }
  
    AbiTagList ReturnTypeAbiTags = makeFunctionReturnTypeTags(FD);
    if (ReturnTypeAbiTags.empty()) {
      // There are no tags for return type, the simplest case.
      mangleName(GD);
      mangleFunctionEncodingBareType(FD);
      return;
    }
  
    // Mangle function name and encoding to temporary buffer.
    // We have to output name and encoding to the same mangler to get the same
    // substitution as it will be in final mangling.
    SmallString<256> FunctionEncodingBuf;
    llvm::raw_svector_ostream FunctionEncodingStream(FunctionEncodingBuf);
    CXXNameMangler FunctionEncodingMangler(*this, FunctionEncodingStream);
    // Output name of the function.
    FunctionEncodingMangler.disableDerivedAbiTags();
    FunctionEncodingMangler.mangleNameWithAbiTags(FD, nullptr);
  
    // Remember length of the function name in the buffer.
    size_t EncodingPositionStart = FunctionEncodingStream.str().size();
    FunctionEncodingMangler.mangleFunctionEncodingBareType(FD);
  
    // Get tags from return type that are not present in function name or
    // encoding.
    const AbiTagList &UsedAbiTags =
        FunctionEncodingMangler.AbiTagsRoot.getSortedUniqueUsedAbiTags();
    AbiTagList AdditionalAbiTags(ReturnTypeAbiTags.size());
    AdditionalAbiTags.erase(
        std::set_difference(ReturnTypeAbiTags.begin(), ReturnTypeAbiTags.end(),
                            UsedAbiTags.begin(), UsedAbiTags.end(),
                            AdditionalAbiTags.begin()),
        AdditionalAbiTags.end());
  
    // Output name with implicit tags and function encoding from temporary buffer.
    mangleNameWithAbiTags(FD, &AdditionalAbiTags);
    Out << FunctionEncodingStream.str().substr(EncodingPositionStart);
  
    // Function encoding could create new substitutions so we have to add
    // temp mangled substitutions to main mangler.
    extendSubstitutions(&FunctionEncodingMangler);
  }
  
  void CXXNameMangler::mangleFunctionEncodingBareType(const FunctionDecl *FD) {
    if (FD->hasAttr<EnableIfAttr>()) {
      FunctionTypeDepthState Saved = FunctionTypeDepth.push();
      Out << "Ua9enable_ifI";
      for (AttrVec::const_iterator I = FD->getAttrs().begin(),
                                   E = FD->getAttrs().end();
           I != E; ++I) {
        EnableIfAttr *EIA = dyn_cast<EnableIfAttr>(*I);
        if (!EIA)
          continue;
        Out << 'X';
        mangleExpression(EIA->getCond());
        Out << 'E';
      }
      Out << 'E';
      FunctionTypeDepth.pop(Saved);
    }
  
    // When mangling an inheriting constructor, the bare function type used is
    // that of the inherited constructor.
    if (auto *CD = dyn_cast<CXXConstructorDecl>(FD))
      if (auto Inherited = CD->getInheritedConstructor())
        FD = Inherited.getConstructor();
  
    // Whether the mangling of a function type includes the return type depends on
    // the context and the nature of the function. The rules for deciding whether
    // the return type is included are:
    //
    //   1. Template functions (names or types) have return types encoded, with
    //   the exceptions listed below.
    //   2. Function types not appearing as part of a function name mangling,
    //   e.g. parameters, pointer types, etc., have return type encoded, with the
    //   exceptions listed below.
    //   3. Non-template function names do not have return types encoded.
    //
    // The exceptions mentioned in (1) and (2) above, for which the return type is
    // never included, are
    //   1. Constructors.
    //   2. Destructors.
    //   3. Conversion operator functions, e.g. operator int.
    bool MangleReturnType = false;
    if (FunctionTemplateDecl *PrimaryTemplate = FD->getPrimaryTemplate()) {
      if (!(isa<CXXConstructorDecl>(FD) || isa<CXXDestructorDecl>(FD) ||
            isa<CXXConversionDecl>(FD)))
        MangleReturnType = true;
  
      // Mangle the type of the primary template.
      FD = PrimaryTemplate->getTemplatedDecl();
    }
  
    mangleBareFunctionType(FD->getType()->castAs<FunctionProtoType>(),
                           MangleReturnType, FD);
  }
  
  static const DeclContext *IgnoreLinkageSpecDecls(const DeclContext *DC) {
    while (isa<LinkageSpecDecl>(DC)) {
      DC = getEffectiveParentContext(DC);
    }
  
    return DC;
  }
  
  /// Return whether a given namespace is the 'std' namespace.
  static bool isStd(const NamespaceDecl *NS) {
    if (!IgnoreLinkageSpecDecls(getEffectiveParentContext(NS))
                                  ->isTranslationUnit())
      return false;
  
    const IdentifierInfo *II = NS->getOriginalNamespace()->getIdentifier();
    return II && II->isStr("std");
  }
  
  // isStdNamespace - Return whether a given decl context is a toplevel 'std'
  // namespace.
  static bool isStdNamespace(const DeclContext *DC) {
    if (!DC->isNamespace())
      return false;
  
    return isStd(cast<NamespaceDecl>(DC));
  }
  
  static const GlobalDecl
  isTemplate(GlobalDecl GD, const TemplateArgumentList *&TemplateArgs) {
    const NamedDecl *ND = cast<NamedDecl>(GD.getDecl());
    // Check if we have a function template.
    if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND)) {
      if (const TemplateDecl *TD = FD->getPrimaryTemplate()) {
        TemplateArgs = FD->getTemplateSpecializationArgs();
        return GD.getWithDecl(TD);
      }
    }
  
    // Check if we have a class template.
    if (const ClassTemplateSpecializationDecl *Spec =
          dyn_cast<ClassTemplateSpecializationDecl>(ND)) {
      TemplateArgs = &Spec->getTemplateArgs();
      return GD.getWithDecl(Spec->getSpecializedTemplate());
    }
  
    // Check if we have a variable template.
    if (const VarTemplateSpecializationDecl *Spec =
            dyn_cast<VarTemplateSpecializationDecl>(ND)) {
      TemplateArgs = &Spec->getTemplateArgs();
      return GD.getWithDecl(Spec->getSpecializedTemplate());
    }
  
    return GlobalDecl();
  }
  
  void CXXNameMangler::mangleName(GlobalDecl GD) {
    const NamedDecl *ND = cast<NamedDecl>(GD.getDecl());
    if (const VarDecl *VD = dyn_cast<VarDecl>(ND)) {
      // Variables should have implicit tags from its type.
      AbiTagList VariableTypeAbiTags = makeVariableTypeTags(VD);
      if (VariableTypeAbiTags.empty()) {
        // Simple case no variable type tags.
        mangleNameWithAbiTags(VD, nullptr);
        return;
      }
  
      // Mangle variable name to null stream to collect tags.
      llvm::raw_null_ostream NullOutStream;
      CXXNameMangler VariableNameMangler(*this, NullOutStream);
      VariableNameMangler.disableDerivedAbiTags();
      VariableNameMangler.mangleNameWithAbiTags(VD, nullptr);
  
      // Get tags from variable type that are not present in its name.
      const AbiTagList &UsedAbiTags =
          VariableNameMangler.AbiTagsRoot.getSortedUniqueUsedAbiTags();
      AbiTagList AdditionalAbiTags(VariableTypeAbiTags.size());
      AdditionalAbiTags.erase(
          std::set_difference(VariableTypeAbiTags.begin(),
                              VariableTypeAbiTags.end(), UsedAbiTags.begin(),
                              UsedAbiTags.end(), AdditionalAbiTags.begin()),
          AdditionalAbiTags.end());
  
      // Output name with implicit tags.
      mangleNameWithAbiTags(VD, &AdditionalAbiTags);
    } else {
      mangleNameWithAbiTags(GD, nullptr);
    }
  }
  
  void CXXNameMangler::mangleNameWithAbiTags(GlobalDecl GD,
                                             const AbiTagList *AdditionalAbiTags) {
    const NamedDecl *ND = cast<NamedDecl>(GD.getDecl());
    //  <name> ::= [<module-name>] <nested-name>
    //         ::= [<module-name>] <unscoped-name>
    //         ::= [<module-name>] <unscoped-template-name> <template-args>
    //         ::= <local-name>
    //
    const DeclContext *DC = getEffectiveDeclContext(ND);
  
    // If this is an extern variable declared locally, the relevant DeclContext
    // is that of the containing namespace, or the translation unit.
    // FIXME: This is a hack; extern variables declared locally should have
    // a proper semantic declaration context!
    if (isLocalContainerContext(DC) && ND->hasLinkage() && !isLambda(ND))
      while (!DC->isNamespace() && !DC->isTranslationUnit())
        DC = getEffectiveParentContext(DC);
    else if (GetLocalClassDecl(ND)) {
      mangleLocalName(GD, AdditionalAbiTags);
      return;
    }
  
    DC = IgnoreLinkageSpecDecls(DC);
  
    if (isLocalContainerContext(DC)) {
      mangleLocalName(GD, AdditionalAbiTags);
      return;
    }
  
    // Do not mangle the owning module for an external linkage declaration.
    // This enables backwards-compatibility with non-modular code, and is
    // a valid choice since conflicts are not permitted by C++ Modules TS
    // [basic.def.odr]/6.2.
    if (!ND->hasExternalFormalLinkage())
      if (Module *M = ND->getOwningModuleForLinkage())
        mangleModuleName(M);
  
    if (DC->isTranslationUnit() || isStdNamespace(DC)) {
      // Check if we have a template.
      const TemplateArgumentList *TemplateArgs = nullptr;
      if (GlobalDecl TD = isTemplate(GD, TemplateArgs)) {
        mangleUnscopedTemplateName(TD, AdditionalAbiTags);
        mangleTemplateArgs(*TemplateArgs);
        return;
      }
  
      mangleUnscopedName(GD, AdditionalAbiTags);
      return;
    }
  
    mangleNestedName(GD, DC, AdditionalAbiTags);
  }
  
  void CXXNameMangler::mangleModuleName(const Module *M) {
    // Implement the C++ Modules TS name mangling proposal; see
    //     https://gcc.gnu.org/wiki/cxx-modules?action=AttachFile
    //
    //   <module-name> ::= W <unscoped-name>+ E
    //                 ::= W <module-subst> <unscoped-name>* E
    Out << 'W';
    mangleModuleNamePrefix(M->Name);
    Out << 'E';
  }
  
  void CXXNameMangler::mangleModuleNamePrefix(StringRef Name) {
    //  <module-subst> ::= _ <seq-id>          # 0 < seq-id < 10
    //                 ::= W <seq-id - 10> _   # otherwise
    auto It = ModuleSubstitutions.find(Name);
    if (It != ModuleSubstitutions.end()) {
      if (It->second < 10)
        Out << '_' << static_cast<char>('0' + It->second);
      else
        Out << 'W' << (It->second - 10) << '_';
      return;
    }
  
    // FIXME: Preserve hierarchy in module names rather than flattening
    // them to strings; use Module*s as substitution keys.
    auto Parts = Name.rsplit('.');
    if (Parts.second.empty())
      Parts.second = Parts.first;
    else
      mangleModuleNamePrefix(Parts.first);
  
    Out << Parts.second.size() << Parts.second;
    ModuleSubstitutions.insert({Name, ModuleSubstitutions.size()});
  }
  
  void CXXNameMangler::mangleTemplateName(const TemplateDecl *TD,
                                          const TemplateArgument *TemplateArgs,
                                          unsigned NumTemplateArgs) {
    const DeclContext *DC = IgnoreLinkageSpecDecls(getEffectiveDeclContext(TD));
  
    if (DC->isTranslationUnit() || isStdNamespace(DC)) {
      mangleUnscopedTemplateName(TD, nullptr);
      mangleTemplateArgs(TemplateArgs, NumTemplateArgs);
    } else {
      mangleNestedName(TD, TemplateArgs, NumTemplateArgs);
    }
  }
  
  void CXXNameMangler::mangleUnscopedName(GlobalDecl GD,
                                          const AbiTagList *AdditionalAbiTags) {
    const NamedDecl *ND = cast<NamedDecl>(GD.getDecl());
    //  <unscoped-name> ::= <unqualified-name>
    //                  ::= St <unqualified-name>   # ::std::
  
    if (isStdNamespace(IgnoreLinkageSpecDecls(getEffectiveDeclContext(ND))))
      Out << "St";
  
    mangleUnqualifiedName(GD, AdditionalAbiTags);
  }
  
  void CXXNameMangler::mangleUnscopedTemplateName(
      GlobalDecl GD, const AbiTagList *AdditionalAbiTags) {
    const TemplateDecl *ND = cast<TemplateDecl>(GD.getDecl());
    //     <unscoped-template-name> ::= <unscoped-name>
    //                              ::= <substitution>
    if (mangleSubstitution(ND))
      return;
  
    // <template-template-param> ::= <template-param>
    if (const auto *TTP = dyn_cast<TemplateTemplateParmDecl>(ND)) {
      assert(!AdditionalAbiTags &&
             "template template param cannot have abi tags");
      mangleTemplateParameter(TTP->getDepth(), TTP->getIndex());
    } else if (isa<BuiltinTemplateDecl>(ND) || isa<ConceptDecl>(ND)) {
      mangleUnscopedName(GD, AdditionalAbiTags);
    } else {
      mangleUnscopedName(GD.getWithDecl(ND->getTemplatedDecl()), AdditionalAbiTags);
    }
  
    addSubstitution(ND);
  }
  
  void CXXNameMangler::mangleUnscopedTemplateName(
      TemplateName Template, const AbiTagList *AdditionalAbiTags) {
    //     <unscoped-template-name> ::= <unscoped-name>
    //                              ::= <substitution>
    if (TemplateDecl *TD = Template.getAsTemplateDecl())
      return mangleUnscopedTemplateName(TD, AdditionalAbiTags);
  
    if (mangleSubstitution(Template))
      return;
  
    assert(!AdditionalAbiTags &&
           "dependent template name cannot have abi tags");
  
    DependentTemplateName *Dependent = Template.getAsDependentTemplateName();
    assert(Dependent && "Not a dependent template name?");
    if (const IdentifierInfo *Id = Dependent->getIdentifier())
      mangleSourceName(Id);
    else
      mangleOperatorName(Dependent->getOperator(), UnknownArity);
  
    addSubstitution(Template);
  }
  
  void CXXNameMangler::mangleFloat(const llvm::APFloat &f) {
    // ABI:
    //   Floating-point literals are encoded using a fixed-length
    //   lowercase hexadecimal string corresponding to the internal
    //   representation (IEEE on Itanium), high-order bytes first,
    //   without leading zeroes. For example: "Lf bf800000 E" is -1.0f
    //   on Itanium.
    // The 'without leading zeroes' thing seems to be an editorial
    // mistake; see the discussion on cxx-abi-dev beginning on
    // 2012-01-16.
  
    // Our requirements here are just barely weird enough to justify
    // using a custom algorithm instead of post-processing APInt::toString().
  
    llvm::APInt valueBits = f.bitcastToAPInt();
    unsigned numCharacters = (valueBits.getBitWidth() + 3) / 4;
    assert(numCharacters != 0);
  
    // Allocate a buffer of the right number of characters.
    SmallVector<char, 20> buffer(numCharacters);
  
    // Fill the buffer left-to-right.
    for (unsigned stringIndex = 0; stringIndex != numCharacters; ++stringIndex) {
      // The bit-index of the next hex digit.
      unsigned digitBitIndex = 4 * (numCharacters - stringIndex - 1);
  
      // Project out 4 bits starting at 'digitIndex'.
      uint64_t hexDigit = valueBits.getRawData()[digitBitIndex / 64];
      hexDigit >>= (digitBitIndex % 64);
      hexDigit &= 0xF;
  
      // Map that over to a lowercase hex digit.
      static const char charForHex[16] = {
        '0', '1', '2', '3', '4', '5', '6', '7',
        '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
      };
      buffer[stringIndex] = charForHex[hexDigit];
    }
  
    Out.write(buffer.data(), numCharacters);
  }
  
  void CXXNameMangler::mangleNumber(const llvm::APSInt &Value) {
    if (Value.isSigned() && Value.isNegative()) {
      Out << 'n';
      Value.abs().print(Out, /*signed*/ false);
    } else {
      Value.print(Out, /*signed*/ false);
    }
  }
  
  void CXXNameMangler::mangleNumber(int64_t Number) {
    //  <number> ::= [n] <non-negative decimal integer>
    if (Number < 0) {
      Out << 'n';
      Number = -Number;
    }
  
    Out << Number;
  }
  
  void CXXNameMangler::mangleCallOffset(int64_t NonVirtual, int64_t Virtual) {
    //  <call-offset>  ::= h <nv-offset> _
    //                 ::= v <v-offset> _
    //  <nv-offset>    ::= <offset number>        # non-virtual base override
    //  <v-offset>     ::= <offset number> _ <virtual offset number>
    //                      # virtual base override, with vcall offset
    if (!Virtual) {
      Out << 'h';
      mangleNumber(NonVirtual);
      Out << '_';
      return;
    }
  
    Out << 'v';
    mangleNumber(NonVirtual);
    Out << '_';
    mangleNumber(Virtual);
    Out << '_';
  }
  
  void CXXNameMangler::manglePrefix(QualType type) {
    if (const auto *TST = type->getAs<TemplateSpecializationType>()) {
      if (!mangleSubstitution(QualType(TST, 0))) {
        mangleTemplatePrefix(TST->getTemplateName());
  
        // FIXME: GCC does not appear to mangle the template arguments when
        // the template in question is a dependent template name. Should we
        // emulate that badness?
        mangleTemplateArgs(TST->getArgs(), TST->getNumArgs());
        addSubstitution(QualType(TST, 0));
      }
    } else if (const auto *DTST =
                   type->getAs<DependentTemplateSpecializationType>()) {
      if (!mangleSubstitution(QualType(DTST, 0))) {
        TemplateName Template = getASTContext().getDependentTemplateName(
            DTST->getQualifier(), DTST->getIdentifier());
        mangleTemplatePrefix(Template);
  
        // FIXME: GCC does not appear to mangle the template arguments when
        // the template in question is a dependent template name. Should we
        // emulate that badness?
        mangleTemplateArgs(DTST->getArgs(), DTST->getNumArgs());
        addSubstitution(QualType(DTST, 0));
      }
    } else {
      // We use the QualType mangle type variant here because it handles
      // substitutions.
      mangleType(type);
    }
  }
  
  /// Mangle everything prior to the base-unresolved-name in an unresolved-name.
  ///
  /// \param recursive - true if this is being called recursively,
  ///   i.e. if there is more prefix "to the right".
  void CXXNameMangler::mangleUnresolvedPrefix(NestedNameSpecifier *qualifier,
                                              bool recursive) {
  
    // x, ::x
    // <unresolved-name> ::= [gs] <base-unresolved-name>
  
    // T::x / decltype(p)::x
    // <unresolved-name> ::= sr <unresolved-type> <base-unresolved-name>
  
    // T::N::x /decltype(p)::N::x
    // <unresolved-name> ::= srN <unresolved-type> <unresolved-qualifier-level>+ E
    //                       <base-unresolved-name>
  
    // A::x, N::y, A<T>::z; "gs" means leading "::"
    // <unresolved-name> ::= [gs] sr <unresolved-qualifier-level>+ E
    //                       <base-unresolved-name>
  
    switch (qualifier->getKind()) {
    case NestedNameSpecifier::Global:
      Out << "gs";
  
      // We want an 'sr' unless this is the entire NNS.
      if (recursive)
        Out << "sr";
  
      // We never want an 'E' here.
      return;
  
    case NestedNameSpecifier::Super:
      llvm_unreachable("Can't mangle __super specifier");
  
    case NestedNameSpecifier::Namespace:
      if (qualifier->getPrefix())
        mangleUnresolvedPrefix(qualifier->getPrefix(),
                               /*recursive*/ true);
      else
        Out << "sr";
      mangleSourceNameWithAbiTags(qualifier->getAsNamespace());
      break;
    case NestedNameSpecifier::NamespaceAlias:
      if (qualifier->getPrefix())
        mangleUnresolvedPrefix(qualifier->getPrefix(),
                               /*recursive*/ true);
      else
        Out << "sr";
      mangleSourceNameWithAbiTags(qualifier->getAsNamespaceAlias());
      break;
  
    case NestedNameSpecifier::TypeSpec:
    case NestedNameSpecifier::TypeSpecWithTemplate: {
      const Type *type = qualifier->getAsType();
  
      // We only want to use an unresolved-type encoding if this is one of:
      //   - a decltype
      //   - a template type parameter
      //   - a template template parameter with arguments
      // In all of these cases, we should have no prefix.
      if (qualifier->getPrefix()) {
        mangleUnresolvedPrefix(qualifier->getPrefix(),
                               /*recursive*/ true);
      } else {
        // Otherwise, all the cases want this.
        Out << "sr";
      }
  
      if (mangleUnresolvedTypeOrSimpleId(QualType(type, 0), recursive ? "N" : ""))
        return;
  
      break;
    }
  
    case NestedNameSpecifier::Identifier:
      // Member expressions can have these without prefixes.
      if (qualifier->getPrefix())
        mangleUnresolvedPrefix(qualifier->getPrefix(),
                               /*recursive*/ true);
      else
        Out << "sr";
  
      mangleSourceName(qualifier->getAsIdentifier());
      // An Identifier has no type information, so we can't emit abi tags for it.
      break;
    }
  
    // If this was the innermost part of the NNS, and we fell out to
    // here, append an 'E'.
    if (!recursive)
      Out << 'E';
  }
  
  /// Mangle an unresolved-name, which is generally used for names which
  /// weren't resolved to specific entities.
  void CXXNameMangler::mangleUnresolvedName(
      NestedNameSpecifier *qualifier, DeclarationName name,
      const TemplateArgumentLoc *TemplateArgs, unsigned NumTemplateArgs,
      unsigned knownArity) {
    if (qualifier) mangleUnresolvedPrefix(qualifier);
    switch (name.getNameKind()) {
      // <base-unresolved-name> ::= <simple-id>
      case DeclarationName::Identifier:
        mangleSourceName(name.getAsIdentifierInfo());
        break;
      // <base-unresolved-name> ::= dn <destructor-name>
      case DeclarationName::CXXDestructorName:
        Out << "dn";
        mangleUnresolvedTypeOrSimpleId(name.getCXXNameType());
        break;
      // <base-unresolved-name> ::= on <operator-name>
      case DeclarationName::CXXConversionFunctionName:
      case DeclarationName::CXXLiteralOperatorName:
      case DeclarationName::CXXOperatorName:
        Out << "on";
        mangleOperatorName(name, knownArity);
        break;
      case DeclarationName::CXXConstructorName:
        llvm_unreachable("Can't mangle a constructor name!");
      case DeclarationName::CXXUsingDirective:
        llvm_unreachable("Can't mangle a using directive name!");
      case DeclarationName::CXXDeductionGuideName:
        llvm_unreachable("Can't mangle a deduction guide name!");
      case DeclarationName::ObjCMultiArgSelector:
      case DeclarationName::ObjCOneArgSelector:
      case DeclarationName::ObjCZeroArgSelector:
        llvm_unreachable("Can't mangle Objective-C selector names here!");
    }
  
    // The <simple-id> and on <operator-name> productions end in an optional
    // <template-args>.
    if (TemplateArgs)
      mangleTemplateArgs(TemplateArgs, NumTemplateArgs);
  }
  
  void CXXNameMangler::mangleUnqualifiedName(GlobalDecl GD,
                                             DeclarationName Name,
                                             unsigned KnownArity,
                                             const AbiTagList *AdditionalAbiTags) {
    const NamedDecl *ND = cast_or_null<NamedDecl>(GD.getDecl());
    unsigned Arity = KnownArity;
    //  <unqualified-name> ::= <operator-name>
    //                     ::= <ctor-dtor-name>
    //                     ::= <source-name>
    switch (Name.getNameKind()) {
    case DeclarationName::Identifier: {
      const IdentifierInfo *II = Name.getAsIdentifierInfo();
  
      // We mangle decomposition declarations as the names of their bindings.
      if (auto *DD = dyn_cast<DecompositionDecl>(ND)) {
        // FIXME: Non-standard mangling for decomposition declarations:
        //
        //  <unqualified-name> ::= DC <source-name>* E
        //
        // These can never be referenced across translation units, so we do
        // not need a cross-vendor mangling for anything other than demanglers.
        // Proposed on cxx-abi-dev on 2016-08-12
        Out << "DC";
        for (auto *BD : DD->bindings())
          mangleSourceName(BD->getDeclName().getAsIdentifierInfo());
        Out << 'E';
        writeAbiTags(ND, AdditionalAbiTags);
        break;
      }
  
      if (auto *GD = dyn_cast<MSGuidDecl>(ND)) {
        // We follow MSVC in mangling GUID declarations as if they were variables
        // with a particular reserved name. Continue the pretense here.
        SmallString<sizeof("_GUID_12345678_1234_1234_1234_1234567890ab")> GUID;
        llvm::raw_svector_ostream GUIDOS(GUID);
        Context.mangleMSGuidDecl(GD, GUIDOS);
        Out << GUID.size() << GUID;
        break;
      }
  
      if (II) {
        // Match GCC's naming convention for internal linkage symbols, for
        // symbols that are not actually visible outside of this TU. GCC
        // distinguishes between internal and external linkage symbols in
        // its mangling, to support cases like this that were valid C++ prior
        // to DR426:
        //
        //   void test() { extern void foo(); }
        //   static void foo();
        //
        // Don't bother with the L marker for names in anonymous namespaces; the
        // 12_GLOBAL__N_1 mangling is quite sufficient there, and this better
        // matches GCC anyway, because GCC does not treat anonymous namespaces as
        // implying internal linkage.
        if (ND && ND->getFormalLinkage() == InternalLinkage &&
            !ND->isExternallyVisible() &&
            getEffectiveDeclContext(ND)->isFileContext() &&
            !ND->isInAnonymousNamespace())
          Out << 'L';
  
        auto *FD = dyn_cast<FunctionDecl>(ND);
        bool IsRegCall = FD &&
                         FD->getType()->castAs<FunctionType>()->getCallConv() ==
                             clang::CC_X86RegCall;
        bool IsDeviceStub =
            FD && FD->hasAttr<CUDAGlobalAttr>() &&
            GD.getKernelReferenceKind() == KernelReferenceKind::Stub;
        if (IsDeviceStub)
          mangleDeviceStubName(II);
        else if (IsRegCall)
          mangleRegCallName(II);
        else
          mangleSourceName(II);
  
        writeAbiTags(ND, AdditionalAbiTags);
        break;
      }
  
      // Otherwise, an anonymous entity.  We must have a declaration.
      assert(ND && "mangling empty name without declaration");
  
      if (const NamespaceDecl *NS = dyn_cast<NamespaceDecl>(ND)) {
        if (NS->isAnonymousNamespace()) {
          // This is how gcc mangles these names.
          Out << "12_GLOBAL__N_1";
          break;
        }
      }
  
      if (const VarDecl *VD = dyn_cast<VarDecl>(ND)) {
        // We must have an anonymous union or struct declaration.
        const RecordDecl *RD = VD->getType()->castAs<RecordType>()->getDecl();
  
        // Itanium C++ ABI 5.1.2:
        //
        //   For the purposes of mangling, the name of an anonymous union is
        //   considered to be the name of the first named data member found by a
        //   pre-order, depth-first, declaration-order walk of the data members of
        //   the anonymous union. If there is no such data member (i.e., if all of
        //   the data members in the union are unnamed), then there is no way for
        //   a program to refer to the anonymous union, and there is therefore no
        //   need to mangle its name.
        assert(RD->isAnonymousStructOrUnion()
               && "Expected anonymous struct or union!");
        const FieldDecl *FD = RD->findFirstNamedDataMember();
  
        // It's actually possible for various reasons for us to get here
        // with an empty anonymous struct / union.  Fortunately, it
        // doesn't really matter what name we generate.
        if (!FD) break;
        assert(FD->getIdentifier() && "Data member name isn't an identifier!");
  
        mangleSourceName(FD->getIdentifier());
        // Not emitting abi tags: internal name anyway.
        break;
      }
  
      // Class extensions have no name as a category, and it's possible
      // for them to be the semantic parent of certain declarations
      // (primarily, tag decls defined within declarations).  Such
      // declarations will always have internal linkage, so the name
      // doesn't really matter, but we shouldn't crash on them.  For
      // safety, just handle all ObjC containers here.
      if (isa<ObjCContainerDecl>(ND))
        break;
  
      // We must have an anonymous struct.
      const TagDecl *TD = cast<TagDecl>(ND);
      if (const TypedefNameDecl *D = TD->getTypedefNameForAnonDecl()) {
        assert(TD->getDeclContext() == D->getDeclContext() &&
               "Typedef should not be in another decl context!");
        assert(D->getDeclName().getAsIdentifierInfo() &&
               "Typedef was not named!");
        mangleSourceName(D->getDeclName().getAsIdentifierInfo());
        assert(!AdditionalAbiTags && "Type cannot have additional abi tags");
        // Explicit abi tags are still possible; take from underlying type, not
        // from typedef.
        writeAbiTags(TD, nullptr);
        break;
      }
  
      // <unnamed-type-name> ::= <closure-type-name>
      //
      // <closure-type-name> ::= Ul <lambda-sig> E [ <nonnegative number> ] _
      // <lambda-sig> ::= <template-param-decl>* <parameter-type>+
      //     # Parameter types or 'v' for 'void'.
      if (const CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(TD)) {
        if (Record->isLambda() && Record->getLambdaManglingNumber()) {
          assert(!AdditionalAbiTags &&
                 "Lambda type cannot have additional abi tags");
          mangleLambda(Record);
          break;
        }
      }
  
      if (TD->isExternallyVisible()) {
        unsigned UnnamedMangle = getASTContext().getManglingNumber(TD);
        Out << "Ut";
        if (UnnamedMangle > 1)
          Out << UnnamedMangle - 2;
        Out << '_';
        writeAbiTags(TD, AdditionalAbiTags);
        break;
      }
  
      // Get a unique id for the anonymous struct. If it is not a real output
      // ID doesn't matter so use fake one.
      unsigned AnonStructId = NullOut ? 0 : Context.getAnonymousStructId(TD);
  
      // Mangle it as a source name in the form
      // [n] $_<id>
      // where n is the length of the string.
      SmallString<8> Str;
      Str += "$_";
      Str += llvm::utostr(AnonStructId);
  
      Out << Str.size();
      Out << Str;
      break;
    }
  
    case DeclarationName::ObjCZeroArgSelector:
    case DeclarationName::ObjCOneArgSelector:
    case DeclarationName::ObjCMultiArgSelector:
      llvm_unreachable("Can't mangle Objective-C selector names here!");
  
    case DeclarationName::CXXConstructorName: {
      const CXXRecordDecl *InheritedFrom = nullptr;
      const TemplateArgumentList *InheritedTemplateArgs = nullptr;
      if (auto Inherited =
              cast<CXXConstructorDecl>(ND)->getInheritedConstructor()) {
        InheritedFrom = Inherited.getConstructor()->getParent();
        InheritedTemplateArgs =
            Inherited.getConstructor()->getTemplateSpecializationArgs();
      }
  
      if (ND == Structor)
        // If the named decl is the C++ constructor we're mangling, use the type
        // we were given.
        mangleCXXCtorType(static_cast<CXXCtorType>(StructorType), InheritedFrom);
      else
        // Otherwise, use the complete constructor name. This is relevant if a
        // class with a constructor is declared within a constructor.
        mangleCXXCtorType(Ctor_Complete, InheritedFrom);
  
      // FIXME: The template arguments are part of the enclosing prefix or
      // nested-name, but it's more convenient to mangle them here.
      if (InheritedTemplateArgs)
        mangleTemplateArgs(*InheritedTemplateArgs);
  
      writeAbiTags(ND, AdditionalAbiTags);
      break;
    }
  
    case DeclarationName::CXXDestructorName:
      if (ND == Structor)
        // If the named decl is the C++ destructor we're mangling, use the type we
        // were given.
        mangleCXXDtorType(static_cast<CXXDtorType>(StructorType));
      else
        // Otherwise, use the complete destructor name. This is relevant if a
        // class with a destructor is declared within a destructor.
        mangleCXXDtorType(Dtor_Complete);
      writeAbiTags(ND, AdditionalAbiTags);
      break;
  
    case DeclarationName::CXXOperatorName:
      if (ND && Arity == UnknownArity) {
        Arity = cast<FunctionDecl>(ND)->getNumParams();
  
        // If we have a member function, we need to include the 'this' pointer.
        if (const auto *MD = dyn_cast<CXXMethodDecl>(ND))
          if (!MD->isStatic())
            Arity++;
      }
      LLVM_FALLTHROUGH;
    case DeclarationName::CXXConversionFunctionName:
    case DeclarationName::CXXLiteralOperatorName:
      mangleOperatorName(Name, Arity);
      writeAbiTags(ND, AdditionalAbiTags);
      break;
  
    case DeclarationName::CXXDeductionGuideName:
      llvm_unreachable("Can't mangle a deduction guide name!");
  
    case DeclarationName::CXXUsingDirective:
      llvm_unreachable("Can't mangle a using directive name!");
    }
  }
  
  void CXXNameMangler::mangleRegCallName(const IdentifierInfo *II) {
    // <source-name> ::= <positive length number> __regcall3__ <identifier>
    // <number> ::= [n] <non-negative decimal integer>
    // <identifier> ::= <unqualified source code identifier>
    Out << II->getLength() + sizeof("__regcall3__") - 1 << "__regcall3__"
        << II->getName();
  }
  
  void CXXNameMangler::mangleDeviceStubName(const IdentifierInfo *II) {
    // <source-name> ::= <positive length number> __device_stub__ <identifier>
    // <number> ::= [n] <non-negative decimal integer>
    // <identifier> ::= <unqualified source code identifier>
    Out << II->getLength() + sizeof("__device_stub__") - 1 << "__device_stub__"
        << II->getName();
  }
  
  void CXXNameMangler::mangleSourceName(const IdentifierInfo *II) {
    // <source-name> ::= <positive length number> <identifier>
    // <number> ::= [n] <non-negative decimal integer>
    // <identifier> ::= <unqualified source code identifier>
    Out << II->getLength() << II->getName();
  }
  
  void CXXNameMangler::mangleNestedName(GlobalDecl GD,
                                        const DeclContext *DC,
                                        const AbiTagList *AdditionalAbiTags,
                                        bool NoFunction) {
    const NamedDecl *ND = cast<NamedDecl>(GD.getDecl());
    // <nested-name>
    //   ::= N [<CV-qualifiers>] [<ref-qualifier>] <prefix> <unqualified-name> E
    //   ::= N [<CV-qualifiers>] [<ref-qualifier>] <template-prefix>
    //       <template-args> E
  
    Out << 'N';
    if (const CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(ND)) {
      Qualifiers MethodQuals = Method->getMethodQualifiers();
      // We do not consider restrict a distinguishing attribute for overloading
      // purposes so we must not mangle it.
      MethodQuals.removeRestrict();
      mangleQualifiers(MethodQuals);
      mangleRefQualifier(Method->getRefQualifier());
    }
  
    // Check if we have a template.
    const TemplateArgumentList *TemplateArgs = nullptr;
    if (GlobalDecl TD = isTemplate(GD, TemplateArgs)) {
      mangleTemplatePrefix(TD, NoFunction);
      mangleTemplateArgs(*TemplateArgs);
    }
    else {
      manglePrefix(DC, NoFunction);
      mangleUnqualifiedName(GD, AdditionalAbiTags);
    }
  
    Out << 'E';
  }
  void CXXNameMangler::mangleNestedName(const TemplateDecl *TD,
                                        const TemplateArgument *TemplateArgs,
                                        unsigned NumTemplateArgs) {
    // <nested-name> ::= N [<CV-qualifiers>] <template-prefix> <template-args> E
  
    Out << 'N';
  
    mangleTemplatePrefix(TD);
    mangleTemplateArgs(TemplateArgs, NumTemplateArgs);
  
    Out << 'E';
  }
  
  static GlobalDecl getParentOfLocalEntity(const DeclContext *DC) {
    GlobalDecl GD;
    // The Itanium spec says:
    // For entities in constructors and destructors, the mangling of the
    // complete object constructor or destructor is used as the base function
    // name, i.e. the C1 or D1 version.
    if (auto *CD = dyn_cast<CXXConstructorDecl>(DC))
      GD = GlobalDecl(CD, Ctor_Complete);
    else if (auto *DD = dyn_cast<CXXDestructorDecl>(DC))
      GD = GlobalDecl(DD, Dtor_Complete);
    else
      GD = GlobalDecl(cast<FunctionDecl>(DC));
    return GD;
  }
  
  void CXXNameMangler::mangleLocalName(GlobalDecl GD,
                                       const AbiTagList *AdditionalAbiTags) {
    const Decl *D = GD.getDecl();
    // <local-name> := Z <function encoding> E <entity name> [<discriminator>]
    //              := Z <function encoding> E s [<discriminator>]
    // <local-name> := Z <function encoding> E d [ <parameter number> ]
    //                 _ <entity name>
    // <discriminator> := _ <non-negative number>
    assert(isa<NamedDecl>(D) || isa<BlockDecl>(D));
    const RecordDecl *RD = GetLocalClassDecl(D);
    const DeclContext *DC = getEffectiveDeclContext(RD ? RD : D);
  
    Out << 'Z';
  
    {
      AbiTagState LocalAbiTags(AbiTags);
  
      if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(DC))
        mangleObjCMethodName(MD);
      else if (const BlockDecl *BD = dyn_cast<BlockDecl>(DC))
        mangleBlockForPrefix(BD);
      else
        mangleFunctionEncoding(getParentOfLocalEntity(DC));
  
      // Implicit ABI tags (from namespace) are not available in the following
      // entity; reset to actually emitted tags, which are available.
      LocalAbiTags.setUsedAbiTags(LocalAbiTags.getEmittedAbiTags());
    }
  
    Out << 'E';
  
    // GCC 5.3.0 doesn't emit derived ABI tags for local names but that seems to
    // be a bug that is fixed in trunk.
  
    if (RD) {
      // The parameter number is omitted for the last parameter, 0 for the
      // second-to-last parameter, 1 for the third-to-last parameter, etc. The
      // <entity name> will of course contain a <closure-type-name>: Its
      // numbering will be local to the particular argument in which it appears
      // -- other default arguments do not affect its encoding.
      const CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(RD);
      if (CXXRD && CXXRD->isLambda()) {
        if (const ParmVarDecl *Parm
                = dyn_cast_or_null<ParmVarDecl>(CXXRD->getLambdaContextDecl())) {
          if (const FunctionDecl *Func
                = dyn_cast<FunctionDecl>(Parm->getDeclContext())) {
            Out << 'd';
            unsigned Num = Func->getNumParams() - Parm->getFunctionScopeIndex();
            if (Num > 1)
              mangleNumber(Num - 2);
            Out << '_';
          }
        }
      }
  
      // Mangle the name relative to the closest enclosing function.
      // equality ok because RD derived from ND above
      if (D == RD)  {
        mangleUnqualifiedName(RD, AdditionalAbiTags);
      } else if (const BlockDecl *BD = dyn_cast<BlockDecl>(D)) {
        manglePrefix(getEffectiveDeclContext(BD), true /*NoFunction*/);
        assert(!AdditionalAbiTags && "Block cannot have additional abi tags");
        mangleUnqualifiedBlock(BD);
      } else {
        const NamedDecl *ND = cast<NamedDecl>(D);
        mangleNestedName(GD, getEffectiveDeclContext(ND), AdditionalAbiTags,
                         true /*NoFunction*/);
      }
    } else if (const BlockDecl *BD = dyn_cast<BlockDecl>(D)) {
      // Mangle a block in a default parameter; see above explanation for
      // lambdas.
      if (const ParmVarDecl *Parm
              = dyn_cast_or_null<ParmVarDecl>(BD->getBlockManglingContextDecl())) {
        if (const FunctionDecl *Func
              = dyn_cast<FunctionDecl>(Parm->getDeclContext())) {
          Out << 'd';
          unsigned Num = Func->getNumParams() - Parm->getFunctionScopeIndex();
          if (Num > 1)
            mangleNumber(Num - 2);
          Out << '_';
        }
      }
  
      assert(!AdditionalAbiTags && "Block cannot have additional abi tags");
      mangleUnqualifiedBlock(BD);
    } else {
      mangleUnqualifiedName(GD, AdditionalAbiTags);
    }
  
    if (const NamedDecl *ND = dyn_cast<NamedDecl>(RD ? RD : D)) {
      unsigned disc;
      if (Context.getNextDiscriminator(ND, disc)) {
        if (disc < 10)
          Out << '_' << disc;
        else
          Out << "__" << disc << '_';
      }
    }
  }
  
  void CXXNameMangler::mangleBlockForPrefix(const BlockDecl *Block) {
    if (GetLocalClassDecl(Block)) {
      mangleLocalName(Block, /* AdditionalAbiTags */ nullptr);
      return;
    }
    const DeclContext *DC = getEffectiveDeclContext(Block);
    if (isLocalContainerContext(DC)) {
      mangleLocalName(Block, /* AdditionalAbiTags */ nullptr);
      return;
    }
    manglePrefix(getEffectiveDeclContext(Block));
    mangleUnqualifiedBlock(Block);
  }
  
  void CXXNameMangler::mangleUnqualifiedBlock(const BlockDecl *Block) {
    if (Decl *Context = Block->getBlockManglingContextDecl()) {
      if ((isa<VarDecl>(Context) || isa<FieldDecl>(Context)) &&
          Context->getDeclContext()->isRecord()) {
        const auto *ND = cast<NamedDecl>(Context);
        if (ND->getIdentifier()) {
          mangleSourceNameWithAbiTags(ND);
          Out << 'M';
        }
      }
    }
  
    // If we have a block mangling number, use it.
    unsigned Number = Block->getBlockManglingNumber();
    // Otherwise, just make up a number. It doesn't matter what it is because
    // the symbol in question isn't externally visible.
    if (!Number)
      Number = Context.getBlockId(Block, false);
    else {
      // Stored mangling numbers are 1-based.
      --Number;
    }
    Out << "Ub";
    if (Number > 0)
      Out << Number - 1;
    Out << '_';
  }
  
  // <template-param-decl>
  //   ::= Ty                              # template type parameter
  //   ::= Tn <type>                       # template non-type parameter
  //   ::= Tt <template-param-decl>* E     # template template parameter
  //   ::= Tp <template-param-decl>        # template parameter pack
  void CXXNameMangler::mangleTemplateParamDecl(const NamedDecl *Decl) {
    if (auto *Ty = dyn_cast<TemplateTypeParmDecl>(Decl)) {
      if (Ty->isParameterPack())
        Out << "Tp";
      Out << "Ty";
    } else if (auto *Tn = dyn_cast<NonTypeTemplateParmDecl>(Decl)) {
      if (Tn->isExpandedParameterPack()) {
        for (unsigned I = 0, N = Tn->getNumExpansionTypes(); I != N; ++I) {
          Out << "Tn";
          mangleType(Tn->getExpansionType(I));
        }
      } else {
        QualType T = Tn->getType();
        if (Tn->isParameterPack()) {
          Out << "Tp";
          if (auto *PackExpansion = T->getAs<PackExpansionType>())
            T = PackExpansion->getPattern();
        }
        Out << "Tn";
        mangleType(T);
      }
    } else if (auto *Tt = dyn_cast<TemplateTemplateParmDecl>(Decl)) {
      if (Tt->isExpandedParameterPack()) {
        for (unsigned I = 0, N = Tt->getNumExpansionTemplateParameters(); I != N;
             ++I) {
          Out << "Tt";
          for (auto *Param : *Tt->getExpansionTemplateParameters(I))
            mangleTemplateParamDecl(Param);
          Out << "E";
        }
      } else {
        if (Tt->isParameterPack())
          Out << "Tp";
        Out << "Tt";
        for (auto *Param : *Tt->getTemplateParameters())
          mangleTemplateParamDecl(Param);
        Out << "E";
      }
    }
  }
  
  void CXXNameMangler::mangleLambda(const CXXRecordDecl *Lambda) {
    // If the context of a closure type is an initializer for a class member
    // (static or nonstatic), it is encoded in a qualified name with a final
    // <prefix> of the form:
    //
    //   <data-member-prefix> := <member source-name> M
    //
    // Technically, the data-member-prefix is part of the <prefix>. However,
    // since a closure type will always be mangled with a prefix, it's easier
    // to emit that last part of the prefix here.
    if (Decl *Context = Lambda->getLambdaContextDecl()) {
      if ((isa<VarDecl>(Context) || isa<FieldDecl>(Context)) &&
          !isa<ParmVarDecl>(Context)) {
        // FIXME: 'inline auto [a, b] = []{ return ... };' does not get a
        // reasonable mangling here.
        if (const IdentifierInfo *Name
              = cast<NamedDecl>(Context)->getIdentifier()) {
          mangleSourceName(Name);
          const TemplateArgumentList *TemplateArgs = nullptr;
          if (isTemplate(cast<NamedDecl>(Context), TemplateArgs))
            mangleTemplateArgs(*TemplateArgs);
          Out << 'M';
        }
      }
    }
  
    Out << "Ul";
    mangleLambdaSig(Lambda);
    Out << "E";
  
    // The number is omitted for the first closure type with a given
    // <lambda-sig> in a given context; it is n-2 for the nth closure type
    // (in lexical order) with that same <lambda-sig> and context.
    //
    // The AST keeps track of the number for us.
    unsigned Number = Lambda->getLambdaManglingNumber();
    assert(Number > 0 && "Lambda should be mangled as an unnamed class");
    if (Number > 1)
      mangleNumber(Number - 2);
    Out << '_';
  }
  
  void CXXNameMangler::mangleLambdaSig(const CXXRecordDecl *Lambda) {
    for (auto *D : Lambda->getLambdaExplicitTemplateParameters())
      mangleTemplateParamDecl(D);
    auto *Proto =
        Lambda->getLambdaTypeInfo()->getType()->castAs<FunctionProtoType>();
    mangleBareFunctionType(Proto, /*MangleReturnType=*/false,
                           Lambda->getLambdaStaticInvoker());
  }
  
  void CXXNameMangler::manglePrefix(NestedNameSpecifier *qualifier) {
    switch (qualifier->getKind()) {
    case NestedNameSpecifier::Global:
      // nothing
      return;
  
    case NestedNameSpecifier::Super:
      llvm_unreachable("Can't mangle __super specifier");
  
    case NestedNameSpecifier::Namespace:
      mangleName(qualifier->getAsNamespace());
      return;
  
    case NestedNameSpecifier::NamespaceAlias:
      mangleName(qualifier->getAsNamespaceAlias()->getNamespace());
      return;
  
    case NestedNameSpecifier::TypeSpec:
    case NestedNameSpecifier::TypeSpecWithTemplate:
      manglePrefix(QualType(qualifier->getAsType(), 0));
      return;
  
    case NestedNameSpecifier::Identifier:
      // Member expressions can have these without prefixes, but that
      // should end up in mangleUnresolvedPrefix instead.
      assert(qualifier->getPrefix());
      manglePrefix(qualifier->getPrefix());
  
      mangleSourceName(qualifier->getAsIdentifier());
      return;
    }
  
    llvm_unreachable("unexpected nested name specifier");
  }
  
  void CXXNameMangler::manglePrefix(const DeclContext *DC, bool NoFunction) {
    //  <prefix> ::= <prefix> <unqualified-name>
    //           ::= <template-prefix> <template-args>
    //           ::= <template-param>
    //           ::= # empty
    //           ::= <substitution>
  
    DC = IgnoreLinkageSpecDecls(DC);
  
    if (DC->isTranslationUnit())
      return;
  
    if (NoFunction && isLocalContainerContext(DC))
      return;
  
    assert(!isLocalContainerContext(DC));
  
    const NamedDecl *ND = cast<NamedDecl>(DC);
    if (mangleSubstitution(ND))
      return;
  
    // Check if we have a template.
    const TemplateArgumentList *TemplateArgs = nullptr;
    if (GlobalDecl TD = isTemplate(ND, TemplateArgs)) {
      mangleTemplatePrefix(TD);
      mangleTemplateArgs(*TemplateArgs);
    } else {
      manglePrefix(getEffectiveDeclContext(ND), NoFunction);
      mangleUnqualifiedName(ND, nullptr);
    }
  
    addSubstitution(ND);
  }
  
  void CXXNameMangler::mangleTemplatePrefix(TemplateName Template) {
    // <template-prefix> ::= <prefix> <template unqualified-name>
    //                   ::= <template-param>
    //                   ::= <substitution>
    if (TemplateDecl *TD = Template.getAsTemplateDecl())
      return mangleTemplatePrefix(TD);
  
    if (QualifiedTemplateName *Qualified = Template.getAsQualifiedTemplateName())
      manglePrefix(Qualified->getQualifier());
  
    if (OverloadedTemplateStorage *Overloaded
                                        = Template.getAsOverloadedTemplate()) {
      mangleUnqualifiedName(GlobalDecl(), (*Overloaded->begin())->getDeclName(),
                            UnknownArity, nullptr);
      return;
    }
  
    DependentTemplateName *Dependent = Template.getAsDependentTemplateName();
    assert(Dependent && "Unknown template name kind?");
    if (NestedNameSpecifier *Qualifier = Dependent->getQualifier())
      manglePrefix(Qualifier);
    mangleUnscopedTemplateName(Template, /* AdditionalAbiTags */ nullptr);
  }
  
  void CXXNameMangler::mangleTemplatePrefix(GlobalDecl GD,
                                            bool NoFunction) {
    const TemplateDecl *ND = cast<TemplateDecl>(GD.getDecl());
    // <template-prefix> ::= <prefix> <template unqualified-name>
    //                   ::= <template-param>
    //                   ::= <substitution>
    // <template-template-param> ::= <template-param>
    //                               <substitution>
  
    if (mangleSubstitution(ND))
      return;
  
    // <template-template-param> ::= <template-param>
    if (const auto *TTP = dyn_cast<TemplateTemplateParmDecl>(ND)) {
      mangleTemplateParameter(TTP->getDepth(), TTP->getIndex());
    } else {
      manglePrefix(getEffectiveDeclContext(ND), NoFunction);
      if (isa<BuiltinTemplateDecl>(ND) || isa<ConceptDecl>(ND))
        mangleUnqualifiedName(GD, nullptr);
      else
        mangleUnqualifiedName(GD.getWithDecl(ND->getTemplatedDecl()), nullptr);
    }
  
    addSubstitution(ND);
  }
  
  /// Mangles a template name under the production <type>.  Required for
  /// template template arguments.
  ///   <type> ::= <class-enum-type>
  ///          ::= <template-param>
  ///          ::= <substitution>
  void CXXNameMangler::mangleType(TemplateName TN) {
    if (mangleSubstitution(TN))
      return;
  
    TemplateDecl *TD = nullptr;
  
    switch (TN.getKind()) {
    case TemplateName::QualifiedTemplate:
      TD = TN.getAsQualifiedTemplateName()->getTemplateDecl();
      goto HaveDecl;
  
    case TemplateName::Template:
      TD = TN.getAsTemplateDecl();
      goto HaveDecl;
  
    HaveDecl:
      if (auto *TTP = dyn_cast<TemplateTemplateParmDecl>(TD))
        mangleTemplateParameter(TTP->getDepth(), TTP->getIndex());
      else
        mangleName(TD);
      break;
  
    case TemplateName::OverloadedTemplate:
    case TemplateName::AssumedTemplate:
      llvm_unreachable("can't mangle an overloaded template name as a <type>");
  
    case TemplateName::DependentTemplate: {
      const DependentTemplateName *Dependent = TN.getAsDependentTemplateName();
      assert(Dependent->isIdentifier());
  
      // <class-enum-type> ::= <name>
      // <name> ::= <nested-name>
      mangleUnresolvedPrefix(Dependent->getQualifier());
      mangleSourceName(Dependent->getIdentifier());
      break;
    }
  
    case TemplateName::SubstTemplateTemplateParm: {
      // Substituted template parameters are mangled as the substituted
      // template.  This will check for the substitution twice, which is
      // fine, but we have to return early so that we don't try to *add*
      // the substitution twice.
      SubstTemplateTemplateParmStorage *subst
        = TN.getAsSubstTemplateTemplateParm();
      mangleType(subst->getReplacement());
      return;
    }
  
    case TemplateName::SubstTemplateTemplateParmPack: {
      // FIXME: not clear how to mangle this!
      // template <template <class> class T...> class A {
      //   template <template <class> class U...> void foo(B<T,U> x...);
      // };
      Out << "_SUBSTPACK_";
      break;
    }
    }
  
    addSubstitution(TN);
  }
  
  bool CXXNameMangler::mangleUnresolvedTypeOrSimpleId(QualType Ty,
                                                      StringRef Prefix) {
    // Only certain other types are valid as prefixes;  enumerate them.
    switch (Ty->getTypeClass()) {
    case Type::Builtin:
    case Type::Complex:
    case Type::Adjusted:
    case Type::Decayed:
    case Type::Pointer:
    case Type::BlockPointer:
    case Type::LValueReference:
    case Type::RValueReference:
    case Type::MemberPointer:
    case Type::ConstantArray:
    case Type::IncompleteArray:
    case Type::VariableArray:
    case Type::DependentSizedArray:
    case Type::DependentAddressSpace:
    case Type::DependentVector:
    case Type::DependentSizedExtVector:
    case Type::Vector:
    case Type::ExtVector:
    case Type::ConstantMatrix:
    case Type::DependentSizedMatrix:
    case Type::FunctionProto:
    case Type::FunctionNoProto:
    case Type::Paren:
    case Type::Attributed:
    case Type::Auto:
    case Type::DeducedTemplateSpecialization:
    case Type::PackExpansion:
    case Type::ObjCObject:
    case Type::ObjCInterface:
    case Type::ObjCObjectPointer:
    case Type::ObjCTypeParam:
    case Type::Atomic:
    case Type::Pipe:
    case Type::MacroQualified:
    case Type::ExtInt:
    case Type::DependentExtInt:
      llvm_unreachable("type is illegal as a nested name specifier");
  
    case Type::SubstTemplateTypeParmPack:
      // FIXME: not clear how to mangle this!
      // template <class T...> class A {
      //   template <class U...> void foo(decltype(T::foo(U())) x...);
      // };
      Out << "_SUBSTPACK_";
      break;
  
    // <unresolved-type> ::= <template-param>
    //                   ::= <decltype>
    //                   ::= <template-template-param> <template-args>
    // (this last is not official yet)
    case Type::TypeOfExpr:
    case Type::TypeOf:
    case Type::Decltype:
    case Type::TemplateTypeParm:
    case Type::UnaryTransform:
    case Type::SubstTemplateTypeParm:
    unresolvedType:
      // Some callers want a prefix before the mangled type.
      Out << Prefix;
  
      // This seems to do everything we want.  It's not really
      // sanctioned for a substituted template parameter, though.
      mangleType(Ty);
  
      // We never want to print 'E' directly after an unresolved-type,
      // so we return directly.
      return true;
  
    case Type::Typedef:
      mangleSourceNameWithAbiTags(cast<TypedefType>(Ty)->getDecl());
      break;
  
    case Type::UnresolvedUsing:
      mangleSourceNameWithAbiTags(
          cast<UnresolvedUsingType>(Ty)->getDecl());
      break;
  
    case Type::Enum:
    case Type::Record:
      mangleSourceNameWithAbiTags(cast<TagType>(Ty)->getDecl());
      break;
  
    case Type::TemplateSpecialization: {
      const TemplateSpecializationType *TST =
          cast<TemplateSpecializationType>(Ty);
      TemplateName TN = TST->getTemplateName();
      switch (TN.getKind()) {
      case TemplateName::Template:
      case TemplateName::QualifiedTemplate: {
        TemplateDecl *TD = TN.getAsTemplateDecl();
  
        // If the base is a template template parameter, this is an
        // unresolved type.
        assert(TD && "no template for template specialization type");
        if (isa<TemplateTemplateParmDecl>(TD))
          goto unresolvedType;
  
        mangleSourceNameWithAbiTags(TD);
        break;
      }
  
      case TemplateName::OverloadedTemplate:
      case TemplateName::AssumedTemplate:
      case TemplateName::DependentTemplate:
        llvm_unreachable("invalid base for a template specialization type");
  
      case TemplateName::SubstTemplateTemplateParm: {
        SubstTemplateTemplateParmStorage *subst =
            TN.getAsSubstTemplateTemplateParm();
        mangleExistingSubstitution(subst->getReplacement());
        break;
      }
  
      case TemplateName::SubstTemplateTemplateParmPack: {
        // FIXME: not clear how to mangle this!
        // template <template <class U> class T...> class A {
        //   template <class U...> void foo(decltype(T<U>::foo) x...);
        // };
        Out << "_SUBSTPACK_";
        break;
      }
      }
  
      mangleTemplateArgs(TST->getArgs(), TST->getNumArgs());
      break;
    }
  
    case Type::InjectedClassName:
      mangleSourceNameWithAbiTags(
          cast<InjectedClassNameType>(Ty)->getDecl());
      break;
  
    case Type::DependentName:
      mangleSourceName(cast<DependentNameType>(Ty)->getIdentifier());
      break;
  
    case Type::DependentTemplateSpecialization: {
      const DependentTemplateSpecializationType *DTST =
          cast<DependentTemplateSpecializationType>(Ty);
      mangleSourceName(DTST->getIdentifier());
      mangleTemplateArgs(DTST->getArgs(), DTST->getNumArgs());
      break;
    }
  
    case Type::Elaborated:
      return mangleUnresolvedTypeOrSimpleId(
          cast<ElaboratedType>(Ty)->getNamedType(), Prefix);
    }
  
    return false;
  }
  
  void CXXNameMangler::mangleOperatorName(DeclarationName Name, unsigned Arity) {
    switch (Name.getNameKind()) {
    case DeclarationName::CXXConstructorName:
    case DeclarationName::CXXDestructorName:
    case DeclarationName::CXXDeductionGuideName:
    case DeclarationName::CXXUsingDirective:
    case DeclarationName::Identifier:
    case DeclarationName::ObjCMultiArgSelector:
    case DeclarationName::ObjCOneArgSelector:
    case DeclarationName::ObjCZeroArgSelector:
      llvm_unreachable("Not an operator name");
  
    case DeclarationName::CXXConversionFunctionName:
      // <operator-name> ::= cv <type>    # (cast)
      Out << "cv";
      mangleType(Name.getCXXNameType());
      break;
  
    case DeclarationName::CXXLiteralOperatorName:
      Out << "li";
      mangleSourceName(Name.getCXXLiteralIdentifier());
      return;
  
    case DeclarationName::CXXOperatorName:
      mangleOperatorName(Name.getCXXOverloadedOperator(), Arity);
      break;
    }
  }
  
  void
  CXXNameMangler::mangleOperatorName(OverloadedOperatorKind OO, unsigned Arity) {
    switch (OO) {
    // <operator-name> ::= nw     # new
    case OO_New: Out << "nw"; break;
    //              ::= na        # new[]
    case OO_Array_New: Out << "na"; break;
    //              ::= dl        # delete
    case OO_Delete: Out << "dl"; break;
    //              ::= da        # delete[]
    case OO_Array_Delete: Out << "da"; break;
    //              ::= ps        # + (unary)
    //              ::= pl        # + (binary or unknown)
    case OO_Plus:
      Out << (Arity == 1? "ps" : "pl"); break;
    //              ::= ng        # - (unary)
    //              ::= mi        # - (binary or unknown)
    case OO_Minus:
      Out << (Arity == 1? "ng" : "mi"); break;
    //              ::= ad        # & (unary)
    //              ::= an        # & (binary or unknown)
    case OO_Amp:
      Out << (Arity == 1? "ad" : "an"); break;
    //              ::= de        # * (unary)
    //              ::= ml        # * (binary or unknown)
    case OO_Star:
      // Use binary when unknown.
      Out << (Arity == 1? "de" : "ml"); break;
    //              ::= co        # ~
    case OO_Tilde: Out << "co"; break;
    //              ::= dv        # /
    case OO_Slash: Out << "dv"; break;
    //              ::= rm        # %
    case OO_Percent: Out << "rm"; break;
    //              ::= or        # |
    case OO_Pipe: Out << "or"; break;
    //              ::= eo        # ^
    case OO_Caret: Out << "eo"; break;
    //              ::= aS        # =
    case OO_Equal: Out << "aS"; break;
    //              ::= pL        # +=
    case OO_PlusEqual: Out << "pL"; break;
    //              ::= mI        # -=
    case OO_MinusEqual: Out << "mI"; break;
    //              ::= mL        # *=
    case OO_StarEqual: Out << "mL"; break;
    //              ::= dV        # /=
    case OO_SlashEqual: Out << "dV"; break;
    //              ::= rM        # %=
    case OO_PercentEqual: Out << "rM"; break;
    //              ::= aN        # &=
    case OO_AmpEqual: Out << "aN"; break;
    //              ::= oR        # |=
    case OO_PipeEqual: Out << "oR"; break;
    //              ::= eO        # ^=
    case OO_CaretEqual: Out << "eO"; break;
    //              ::= ls        # <<
    case OO_LessLess: Out << "ls"; break;
    //              ::= rs        # >>
    case OO_GreaterGreater: Out << "rs"; break;
    //              ::= lS        # <<=
    case OO_LessLessEqual: Out << "lS"; break;
    //              ::= rS        # >>=
    case OO_GreaterGreaterEqual: Out << "rS"; break;
    //              ::= eq        # ==
    case OO_EqualEqual: Out << "eq"; break;
    //              ::= ne        # !=
    case OO_ExclaimEqual: Out << "ne"; break;
    //              ::= lt        # <
    case OO_Less: Out << "lt"; break;
    //              ::= gt        # >
    case OO_Greater: Out << "gt"; break;
    //              ::= le        # <=
    case OO_LessEqual: Out << "le"; break;
    //              ::= ge        # >=
    case OO_GreaterEqual: Out << "ge"; break;
    //              ::= nt        # !
    case OO_Exclaim: Out << "nt"; break;
    //              ::= aa        # &&
    case OO_AmpAmp: Out << "aa"; break;
    //              ::= oo        # ||
    case OO_PipePipe: Out << "oo"; break;
    //              ::= pp        # ++
    case OO_PlusPlus: Out << "pp"; break;
    //              ::= mm        # --
    case OO_MinusMinus: Out << "mm"; break;
    //              ::= cm        # ,
    case OO_Comma: Out << "cm"; break;
    //              ::= pm        # ->*
    case OO_ArrowStar: Out << "pm"; break;
    //              ::= pt        # ->
    case OO_Arrow: Out << "pt"; break;
    //              ::= cl        # ()
    case OO_Call: Out << "cl"; break;
    //              ::= ix        # []
    case OO_Subscript: Out << "ix"; break;
  
    //              ::= qu        # ?
    // The conditional operator can't be overloaded, but we still handle it when
    // mangling expressions.
    case OO_Conditional: Out << "qu"; break;
    // Proposal on cxx-abi-dev, 2015-10-21.
    //              ::= aw        # co_await
    case OO_Coawait: Out << "aw"; break;
    // Proposed in cxx-abi github issue 43.
    //              ::= ss        # <=>
    case OO_Spaceship: Out << "ss"; break;
  
    case OO_None:
    case NUM_OVERLOADED_OPERATORS:
      llvm_unreachable("Not an overloaded operator");
    }
  }
  
  void CXXNameMangler::mangleQualifiers(Qualifiers Quals, const DependentAddressSpaceType *DAST) {
    // Vendor qualifiers come first and if they are order-insensitive they must
    // be emitted in reversed alphabetical order, see Itanium ABI 5.1.5.
  
    // <type> ::= U <addrspace-expr>
    if (DAST) {
      Out << "U2ASI";
      mangleExpression(DAST->getAddrSpaceExpr());
      Out << "E";
    }
  
    // Address space qualifiers start with an ordinary letter.
    if (Quals.hasAddressSpace()) {
      // Address space extension:
      //
      //   <type> ::= U <target-addrspace>
      //   <type> ::= U <OpenCL-addrspace>
      //   <type> ::= U <CUDA-addrspace>
  
      SmallString<64> ASString;
      LangAS AS = Quals.getAddressSpace();
  
      if (Context.getASTContext().addressSpaceMapManglingFor(AS)) {
        //  <target-addrspace> ::= "AS" <address-space-number>
        unsigned TargetAS = Context.getASTContext().getTargetAddressSpace(AS);
        if (TargetAS != 0)
          ASString = "AS" + llvm::utostr(TargetAS);
      } else {
        switch (AS) {
        default: llvm_unreachable("Not a language specific address space");
        //  <OpenCL-addrspace> ::= "CL" [ "global" | "local" | "constant" |
        //                                "private"| "generic" | "device" |
        //                                "host" ]
        case LangAS::opencl_global:
          ASString = "CLglobal";
          break;
        case LangAS::opencl_global_device:
          ASString = "CLdevice";
          break;
        case LangAS::opencl_global_host:
          ASString = "CLhost";
          break;
        case LangAS::opencl_local:
          ASString = "CLlocal";
          break;
        case LangAS::opencl_constant:
          ASString = "CLconstant";
          break;
        case LangAS::opencl_private:
          ASString = "CLprivate";
          break;
        case LangAS::opencl_generic:
          ASString = "CLgeneric";
          break;
        //  <CUDA-addrspace> ::= "CU" [ "device" | "constant" | "shared" ]
        case LangAS::cuda_device:
          ASString = "CUdevice";
          break;
        case LangAS::cuda_constant:
          ASString = "CUconstant";
          break;
        case LangAS::cuda_shared:
          ASString = "CUshared";
          break;
        //  <ptrsize-addrspace> ::= [ "ptr32_sptr" | "ptr32_uptr" | "ptr64" ]
        case LangAS::ptr32_sptr:
          ASString = "ptr32_sptr";
          break;
        case LangAS::ptr32_uptr:
          ASString = "ptr32_uptr";
          break;
        case LangAS::ptr64:
          ASString = "ptr64";
          break;
        }
      }
      if (!ASString.empty())
        mangleVendorQualifier(ASString);
    }
  
    // The ARC ownership qualifiers start with underscores.
    // Objective-C ARC Extension:
    //
    //   <type> ::= U "__strong"
    //   <type> ::= U "__weak"
    //   <type> ::= U "__autoreleasing"
    //
    // Note: we emit __weak first to preserve the order as
    // required by the Itanium ABI.
    if (Quals.getObjCLifetime() == Qualifiers::OCL_Weak)
      mangleVendorQualifier("__weak");
  
    // __unaligned (from -fms-extensions)
    if (Quals.hasUnaligned())
      mangleVendorQualifier("__unaligned");
  
    // Remaining ARC ownership qualifiers.
    switch (Quals.getObjCLifetime()) {
    case Qualifiers::OCL_None:
      break;
  
    case Qualifiers::OCL_Weak:
      // Do nothing as we already handled this case above.
      break;
  
    case Qualifiers::OCL_Strong:
      mangleVendorQualifier("__strong");
      break;
  
    case Qualifiers::OCL_Autoreleasing:
      mangleVendorQualifier("__autoreleasing");
      break;
  
    case Qualifiers::OCL_ExplicitNone:
      // The __unsafe_unretained qualifier is *not* mangled, so that
      // __unsafe_unretained types in ARC produce the same manglings as the
      // equivalent (but, naturally, unqualified) types in non-ARC, providing
      // better ABI compatibility.
      //
      // It's safe to do this because unqualified 'id' won't show up
      // in any type signatures that need to be mangled.
      break;
    }
  
    // <CV-qualifiers> ::= [r] [V] [K]    # restrict (C99), volatile, const
    if (Quals.hasRestrict())
      Out << 'r';
    if (Quals.hasVolatile())
      Out << 'V';
    if (Quals.hasConst())
      Out << 'K';
  }
  
  void CXXNameMangler::mangleVendorQualifier(StringRef name) {
    Out << 'U' << name.size() << name;
  }
  
  void CXXNameMangler::mangleRefQualifier(RefQualifierKind RefQualifier) {
    // <ref-qualifier> ::= R                # lvalue reference
    //                 ::= O                # rvalue-reference
    switch (RefQualifier) {
    case RQ_None:
      break;
  
    case RQ_LValue:
      Out << 'R';
      break;
  
    case RQ_RValue:
      Out << 'O';
      break;
    }
  }
  
  void CXXNameMangler::mangleObjCMethodName(const ObjCMethodDecl *MD) {
    Context.mangleObjCMethodNameAsSourceName(MD, Out);
  }
  
  static bool isTypeSubstitutable(Qualifiers Quals, const Type *Ty,
                                  ASTContext &Ctx) {
    if (Quals)
      return true;
    if (Ty->isSpecificBuiltinType(BuiltinType::ObjCSel))
      return true;
    if (Ty->isOpenCLSpecificType())
      return true;
    if (Ty->isBuiltinType())
      return false;
    // Through to Clang 6.0, we accidentally treated undeduced auto types as
    // substitution candidates.
    if (Ctx.getLangOpts().getClangABICompat() > LangOptions::ClangABI::Ver6 &&
        isa<AutoType>(Ty))
      return false;
    return true;
  }
  
  void CXXNameMangler::mangleType(QualType T) {
    // If our type is instantiation-dependent but not dependent, we mangle
    // it as it was written in the source, removing any top-level sugar.
    // Otherwise, use the canonical type.
    //
    // FIXME: This is an approximation of the instantiation-dependent name
    // mangling rules, since we should really be using the type as written and
    // augmented via semantic analysis (i.e., with implicit conversions and
    // default template arguments) for any instantiation-dependent type.
    // Unfortunately, that requires several changes to our AST:
    //   - Instantiation-dependent TemplateSpecializationTypes will need to be
    //     uniqued, so that we can handle substitutions properly
    //   - Default template arguments will need to be represented in the
    //     TemplateSpecializationType, since they need to be mangled even though
    //     they aren't written.
    //   - Conversions on non-type template arguments need to be expressed, since
    //     they can affect the mangling of sizeof/alignof.
    //
    // FIXME: This is wrong when mapping to the canonical type for a dependent
    // type discards instantiation-dependent portions of the type, such as for:
    //
    //   template<typename T, int N> void f(T (&)[sizeof(N)]);
    //   template<typename T> void f(T() throw(typename T::type)); (pre-C++17)
    //
    // It's also wrong in the opposite direction when instantiation-dependent,
    // canonically-equivalent types differ in some irrelevant portion of inner
    // type sugar. In such cases, we fail to form correct substitutions, eg:
    //
    //   template<int N> void f(A<sizeof(N)> *, A<sizeof(N)> (*));
    //
    // We should instead canonicalize the non-instantiation-dependent parts,
    // regardless of whether the type as a whole is dependent or instantiation
    // dependent.
    if (!T->isInstantiationDependentType() || T->isDependentType())
      T = T.getCanonicalType();
    else {
      // Desugar any types that are purely sugar.
      do {
        // Don't desugar through template specialization types that aren't
        // type aliases. We need to mangle the template arguments as written.
        if (const TemplateSpecializationType *TST
                                        = dyn_cast<TemplateSpecializationType>(T))
          if (!TST->isTypeAlias())
            break;
  
        QualType Desugared
          = T.getSingleStepDesugaredType(Context.getASTContext());
        if (Desugared == T)
          break;
  
        T = Desugared;
      } while (true);
    }
    SplitQualType split = T.split();
    Qualifiers quals = split.Quals;
    const Type *ty = split.Ty;
  
    bool isSubstitutable =
      isTypeSubstitutable(quals, ty, Context.getASTContext());
    if (isSubstitutable && mangleSubstitution(T))
      return;
  
    // If we're mangling a qualified array type, push the qualifiers to
    // the element type.
    if (quals && isa<ArrayType>(T)) {
      ty = Context.getASTContext().getAsArrayType(T);
      quals = Qualifiers();
  
      // Note that we don't update T: we want to add the
      // substitution at the original type.
    }
  
    if (quals || ty->isDependentAddressSpaceType()) {
      if (const DependentAddressSpaceType *DAST =
          dyn_cast<DependentAddressSpaceType>(ty)) {
        SplitQualType splitDAST = DAST->getPointeeType().split();
        mangleQualifiers(splitDAST.Quals, DAST);
        mangleType(QualType(splitDAST.Ty, 0));
      } else {
        mangleQualifiers(quals);
  
        // Recurse:  even if the qualified type isn't yet substitutable,
        // the unqualified type might be.
        mangleType(QualType(ty, 0));
      }
    } else {
      switch (ty->getTypeClass()) {
  #define ABSTRACT_TYPE(CLASS, PARENT)
  #define NON_CANONICAL_TYPE(CLASS, PARENT) \
      case Type::CLASS: \
        llvm_unreachable("can't mangle non-canonical type " #CLASS "Type"); \
        return;
  #define TYPE(CLASS, PARENT) \
      case Type::CLASS: \
        mangleType(static_cast<const CLASS##Type*>(ty)); \
        break;
  #include "clang/AST/TypeNodes.inc"
      }
    }
  
    // Add the substitution.
    if (isSubstitutable)
      addSubstitution(T);
  }
  
  void CXXNameMangler::mangleNameOrStandardSubstitution(const NamedDecl *ND) {
    if (!mangleStandardSubstitution(ND))
      mangleName(ND);
  }
  
  void CXXNameMangler::mangleType(const BuiltinType *T) {
    //  <type>         ::= <builtin-type>
    //  <builtin-type> ::= v  # void
    //                 ::= w  # wchar_t
    //                 ::= b  # bool
    //                 ::= c  # char
    //                 ::= a  # signed char
    //                 ::= h  # unsigned char
    //                 ::= s  # short
    //                 ::= t  # unsigned short
    //                 ::= i  # int
    //                 ::= j  # unsigned int
    //                 ::= l  # long
    //                 ::= m  # unsigned long
    //                 ::= x  # long long, __int64
    //                 ::= y  # unsigned long long, __int64
    //                 ::= n  # __int128
    //                 ::= o  # unsigned __int128
    //                 ::= f  # float
    //                 ::= d  # double
    //                 ::= e  # long double, __float80
    //                 ::= g  # __float128
    // UNSUPPORTED:    ::= Dd # IEEE 754r decimal floating point (64 bits)
    // UNSUPPORTED:    ::= De # IEEE 754r decimal floating point (128 bits)
    // UNSUPPORTED:    ::= Df # IEEE 754r decimal floating point (32 bits)
    //                 ::= Dh # IEEE 754r half-precision floating point (16 bits)
    //                 ::= DF <number> _ # ISO/IEC TS 18661 binary floating point type _FloatN (N bits);
    //                 ::= Di # char32_t
    //                 ::= Ds # char16_t
    //                 ::= Dn # std::nullptr_t (i.e., decltype(nullptr))
    //                 ::= u <source-name>    # vendor extended type
    std::string type_name;
    switch (T->getKind()) {
    case BuiltinType::Void:
      Out << 'v';
      break;
    case BuiltinType::Bool:
      Out << 'b';
      break;
    case BuiltinType::Char_U:
    case BuiltinType::Char_S:
      Out << 'c';
      break;
    case BuiltinType::UChar:
      Out << 'h';
      break;
    case BuiltinType::UShort:
      Out << 't';
      break;
    case BuiltinType::UInt:
      Out << 'j';
      break;
    case BuiltinType::ULong:
      Out << 'm';
      break;
    case BuiltinType::ULongLong:
      Out << 'y';
      break;
    case BuiltinType::UInt128:
      Out << 'o';
      break;
    case BuiltinType::SChar:
      Out << 'a';
      break;
    case BuiltinType::WChar_S:
    case BuiltinType::WChar_U:
      Out << 'w';
      break;
    case BuiltinType::Char8:
      Out << "Du";
      break;
    case BuiltinType::Char16:
      Out << "Ds";
      break;
    case BuiltinType::Char32:
      Out << "Di";
      break;
    case BuiltinType::Short:
      Out << 's';
      break;
    case BuiltinType::Int:
      Out << 'i';
      break;
    case BuiltinType::Long:
      Out << 'l';
      break;
    case BuiltinType::LongLong:
      Out << 'x';
      break;
    case BuiltinType::Int128:
      Out << 'n';
      break;
    case BuiltinType::Float16:
      Out << "DF16_";
      break;
    case BuiltinType::ShortAccum:
    case BuiltinType::Accum:
    case BuiltinType::LongAccum:
    case BuiltinType::UShortAccum:
    case BuiltinType::UAccum:
    case BuiltinType::ULongAccum:
    case BuiltinType::ShortFract:
    case BuiltinType::Fract:
    case BuiltinType::LongFract:
    case BuiltinType::UShortFract:
    case BuiltinType::UFract:
    case BuiltinType::ULongFract:
    case BuiltinType::SatShortAccum:
    case BuiltinType::SatAccum:
    case BuiltinType::SatLongAccum:
    case BuiltinType::SatUShortAccum:
    case BuiltinType::SatUAccum:
    case BuiltinType::SatULongAccum:
    case BuiltinType::SatShortFract:
    case BuiltinType::SatFract:
    case BuiltinType::SatLongFract:
    case BuiltinType::SatUShortFract:
    case BuiltinType::SatUFract:
    case BuiltinType::SatULongFract:
      llvm_unreachable("Fixed point types are disabled for c++");
    case BuiltinType::Half:
      Out << "Dh";
      break;
    case BuiltinType::Float:
      Out << 'f';
      break;
    case BuiltinType::Double:
      Out << 'd';
      break;
    case BuiltinType::LongDouble: {
      const TargetInfo *TI = getASTContext().getLangOpts().OpenMP &&
                                     getASTContext().getLangOpts().OpenMPIsDevice
                                 ? getASTContext().getAuxTargetInfo()
                                 : &getASTContext().getTargetInfo();
      Out << TI->getLongDoubleMangling();
      break;
    }
    case BuiltinType::Float128: {
      const TargetInfo *TI = getASTContext().getLangOpts().OpenMP &&
                                     getASTContext().getLangOpts().OpenMPIsDevice
                                 ? getASTContext().getAuxTargetInfo()
                                 : &getASTContext().getTargetInfo();
      Out << TI->getFloat128Mangling();
      break;
    }
    case BuiltinType::BFloat16: {
      const TargetInfo *TI = &getASTContext().getTargetInfo();
      Out << TI->getBFloat16Mangling();
      break;
    }
    case BuiltinType::NullPtr:
      Out << "Dn";
      break;
  
  #define BUILTIN_TYPE(Id, SingletonId)
  #define PLACEHOLDER_TYPE(Id, SingletonId) \
    case BuiltinType::Id:
  #include "clang/AST/BuiltinTypes.def"
    case BuiltinType::Dependent:
      if (!NullOut)
        llvm_unreachable("mangling a placeholder type");
      break;
    case BuiltinType::ObjCId:
      Out << "11objc_object";
      break;
    case BuiltinType::ObjCClass:
      Out << "10objc_class";
      break;
    case BuiltinType::ObjCSel:
      Out << "13objc_selector";
      break;
  #define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
    case BuiltinType::Id: \
      type_name = "ocl_" #ImgType "_" #Suffix; \
      Out << type_name.size() << type_name; \
      break;
  #include "clang/Basic/OpenCLImageTypes.def"
    case BuiltinType::OCLSampler:
      Out << "11ocl_sampler";
      break;
    case BuiltinType::OCLEvent:
      Out << "9ocl_event";
      break;
    case BuiltinType::OCLClkEvent:
      Out << "12ocl_clkevent";
      break;
    case BuiltinType::OCLQueue:
      Out << "9ocl_queue";
      break;
    case BuiltinType::OCLReserveID:
      Out << "13ocl_reserveid";
      break;
  #define EXT_OPAQUE_TYPE(ExtType, Id, Ext) \
    case BuiltinType::Id: \
      type_name = "ocl_" #ExtType; \
      Out << type_name.size() << type_name; \
      break;
  #include "clang/Basic/OpenCLExtensionTypes.def"
    // The SVE types are effectively target-specific.  The mangling scheme
    // is defined in the appendices to the Procedure Call Standard for the
    // Arm Architecture.
  #define SVE_VECTOR_TYPE(InternalName, MangledName, Id, SingletonId, NumEls,    \
                          ElBits, IsSigned, IsFP, IsBF)                          \
    case BuiltinType::Id:                                                        \
      type_name = MangledName;                                                   \
      Out << (type_name == InternalName ? "u" : "") << type_name.size()          \
          << type_name;                                                          \
      break;
  #define SVE_PREDICATE_TYPE(InternalName, MangledName, Id, SingletonId, NumEls) \
    case BuiltinType::Id:                                                        \
      type_name = MangledName;                                                   \
      Out << (type_name == InternalName ? "u" : "") << type_name.size()          \
          << type_name;                                                          \
      break;
  #include "clang/Basic/AArch64SVEACLETypes.def"
  #define PPC_MMA_VECTOR_TYPE(Name, Id, Size) \
    case BuiltinType::Id: \
      type_name = #Name; \
      Out << 'u' << type_name.size() << type_name; \
      break;
  #include "clang/Basic/PPCTypes.def"
    }
  }
  
  StringRef CXXNameMangler::getCallingConvQualifierName(CallingConv CC) {
    switch (CC) {
    case CC_C:
      return "";
  
    case CC_X86VectorCall:
    case CC_X86Pascal:
    case CC_X86RegCall:
    case CC_AAPCS:
    case CC_AAPCS_VFP:
    case CC_AArch64VectorCall:
    case CC_IntelOclBicc:
    case CC_SpirFunction:
    case CC_OpenCLKernel:
    case CC_PreserveMost:
    case CC_PreserveAll:
      // FIXME: we should be mangling all of the above.
      return "";
  
    case CC_X86ThisCall:
      // FIXME: To match mingw GCC, thiscall should only be mangled in when it is
      // used explicitly. At this point, we don't have that much information in
      // the AST, since clang tends to bake the convention into the canonical
      // function type. thiscall only rarely used explicitly, so don't mangle it
      // for now.
      return "";
  
    case CC_X86StdCall:
      return "stdcall";
    case CC_X86FastCall:
      return "fastcall";
    case CC_X86_64SysV:
      return "sysv_abi";
    case CC_Win64:
      return "ms_abi";
    case CC_Swift:
      return "swiftcall";
    }
    llvm_unreachable("bad calling convention");
  }
  
  void CXXNameMangler::mangleExtFunctionInfo(const FunctionType *T) {
    // Fast path.
    if (T->getExtInfo() == FunctionType::ExtInfo())
      return;
  
    // Vendor-specific qualifiers are emitted in reverse alphabetical order.
    // This will get more complicated in the future if we mangle other
    // things here; but for now, since we mangle ns_returns_retained as
    // a qualifier on the result type, we can get away with this:
    StringRef CCQualifier = getCallingConvQualifierName(T->getExtInfo().getCC());
    if (!CCQualifier.empty())
      mangleVendorQualifier(CCQualifier);
  
    // FIXME: regparm
    // FIXME: noreturn
  }
  
  void
  CXXNameMangler::mangleExtParameterInfo(FunctionProtoType::ExtParameterInfo PI) {
    // Vendor-specific qualifiers are emitted in reverse alphabetical order.
  
    // Note that these are *not* substitution candidates.  Demanglers might
    // have trouble with this if the parameter type is fully substituted.
  
    switch (PI.getABI()) {
    case ParameterABI::Ordinary:
      break;
  
    // All of these start with "swift", so they come before "ns_consumed".
    case ParameterABI::SwiftContext:
    case ParameterABI::SwiftErrorResult:
    case ParameterABI::SwiftIndirectResult:
      mangleVendorQualifier(getParameterABISpelling(PI.getABI()));
      break;
    }
  
    if (PI.isConsumed())
      mangleVendorQualifier("ns_consumed");
  
    if (PI.isNoEscape())
      mangleVendorQualifier("noescape");
  }
  
  // <type>          ::= <function-type>
  // <function-type> ::= [<CV-qualifiers>] F [Y]
  //                      <bare-function-type> [<ref-qualifier>] E
  void CXXNameMangler::mangleType(const FunctionProtoType *T) {
    mangleExtFunctionInfo(T);
  
    // Mangle CV-qualifiers, if present.  These are 'this' qualifiers,
    // e.g. "const" in "int (A::*)() const".
    mangleQualifiers(T->getMethodQuals());
  
    // Mangle instantiation-dependent exception-specification, if present,
    // per cxx-abi-dev proposal on 2016-10-11.
    if (T->hasInstantiationDependentExceptionSpec()) {
      if (isComputedNoexcept(T->getExceptionSpecType())) {
        Out << "DO";
        mangleExpression(T->getNoexceptExpr());
        Out << "E";
      } else {
        assert(T->getExceptionSpecType() == EST_Dynamic);
        Out << "Dw";
        for (auto ExceptTy : T->exceptions())
          mangleType(ExceptTy);
        Out << "E";
      }
    } else if (T->isNothrow()) {
      Out << "Do";
    }
  
    Out << 'F';
  
    // FIXME: We don't have enough information in the AST to produce the 'Y'
    // encoding for extern "C" function types.
    mangleBareFunctionType(T, /*MangleReturnType=*/true);
  
    // Mangle the ref-qualifier, if present.
    mangleRefQualifier(T->getRefQualifier());
  
    Out << 'E';
  }
  
  void CXXNameMangler::mangleType(const FunctionNoProtoType *T) {
    // Function types without prototypes can arise when mangling a function type
    // within an overloadable function in C. We mangle these as the absence of any
    // parameter types (not even an empty parameter list).
    Out << 'F';
  
    FunctionTypeDepthState saved = FunctionTypeDepth.push();
  
    FunctionTypeDepth.enterResultType();
    mangleType(T->getReturnType());
    FunctionTypeDepth.leaveResultType();
  
    FunctionTypeDepth.pop(saved);
    Out << 'E';
  }
  
  void CXXNameMangler::mangleBareFunctionType(const FunctionProtoType *Proto,
                                              bool MangleReturnType,
                                              const FunctionDecl *FD) {
    // Record that we're in a function type.  See mangleFunctionParam
    // for details on what we're trying to achieve here.
    FunctionTypeDepthState saved = FunctionTypeDepth.push();
  
    // <bare-function-type> ::= <signature type>+
    if (MangleReturnType) {
      FunctionTypeDepth.enterResultType();
  
      // Mangle ns_returns_retained as an order-sensitive qualifier here.
      if (Proto->getExtInfo().getProducesResult() && FD == nullptr)
        mangleVendorQualifier("ns_returns_retained");
  
      // Mangle the return type without any direct ARC ownership qualifiers.
      QualType ReturnTy = Proto->getReturnType();
      if (ReturnTy.getObjCLifetime()) {
        auto SplitReturnTy = ReturnTy.split();
        SplitReturnTy.Quals.removeObjCLifetime();
        ReturnTy = getASTContext().getQualifiedType(SplitReturnTy);
      }
      mangleType(ReturnTy);
  
      FunctionTypeDepth.leaveResultType();
    }
  
    if (Proto->getNumParams() == 0 && !Proto->isVariadic()) {
      //   <builtin-type> ::= v   # void
      Out << 'v';
  
      FunctionTypeDepth.pop(saved);
      return;
    }
  
    assert(!FD || FD->getNumParams() == Proto->getNumParams());
    for (unsigned I = 0, E = Proto->getNumParams(); I != E; ++I) {
      // Mangle extended parameter info as order-sensitive qualifiers here.
      if (Proto->hasExtParameterInfos() && FD == nullptr) {
        mangleExtParameterInfo(Proto->getExtParameterInfo(I));
      }
  
      // Mangle the type.
      QualType ParamTy = Proto->getParamType(I);
      mangleType(Context.getASTContext().getSignatureParameterType(ParamTy));
  
      if (FD) {
        if (auto *Attr = FD->getParamDecl(I)->getAttr<PassObjectSizeAttr>()) {
          // Attr can only take 1 character, so we can hardcode the length below.
          assert(Attr->getType() <= 9 && Attr->getType() >= 0);
          if (Attr->isDynamic())
            Out << "U25pass_dynamic_object_size" << Attr->getType();
          else
            Out << "U17pass_object_size" << Attr->getType();
        }
      }
    }
  
    FunctionTypeDepth.pop(saved);
  
    // <builtin-type>      ::= z  # ellipsis
    if (Proto->isVariadic())
      Out << 'z';
  }
  
  // <type>            ::= <class-enum-type>
  // <class-enum-type> ::= <name>
  void CXXNameMangler::mangleType(const UnresolvedUsingType *T) {
    mangleName(T->getDecl());
  }
  
  // <type>            ::= <class-enum-type>
  // <class-enum-type> ::= <name>
  void CXXNameMangler::mangleType(const EnumType *T) {
    mangleType(static_cast<const TagType*>(T));
  }
  void CXXNameMangler::mangleType(const RecordType *T) {
    mangleType(static_cast<const TagType*>(T));
  }
  void CXXNameMangler::mangleType(const TagType *T) {
    mangleName(T->getDecl());
  }
  
  // <type>       ::= <array-type>
  // <array-type> ::= A <positive dimension number> _ <element type>
  //              ::= A [<dimension expression>] _ <element type>
  void CXXNameMangler::mangleType(const ConstantArrayType *T) {
    Out << 'A' << T->getSize() << '_';
    mangleType(T->getElementType());
  }
  void CXXNameMangler::mangleType(const VariableArrayType *T) {
    Out << 'A';
    // decayed vla types (size 0) will just be skipped.
    if (T->getSizeExpr())
      mangleExpression(T->getSizeExpr());
    Out << '_';
    mangleType(T->getElementType());
  }
  void CXXNameMangler::mangleType(const DependentSizedArrayType *T) {
    Out << 'A';
    mangleExpression(T->getSizeExpr());
    Out << '_';
    mangleType(T->getElementType());
  }
  void CXXNameMangler::mangleType(const IncompleteArrayType *T) {
    Out << "A_";
    mangleType(T->getElementType());
  }
  
  // <type>                   ::= <pointer-to-member-type>
  // <pointer-to-member-type> ::= M <class type> <member type>
  void CXXNameMangler::mangleType(const MemberPointerType *T) {
    Out << 'M';
    mangleType(QualType(T->getClass(), 0));
    QualType PointeeType = T->getPointeeType();
    if (const FunctionProtoType *FPT = dyn_cast<FunctionProtoType>(PointeeType)) {
      mangleType(FPT);
  
      // Itanium C++ ABI 5.1.8:
      //
      //   The type of a non-static member function is considered to be different,
      //   for the purposes of substitution, from the type of a namespace-scope or
      //   static member function whose type appears similar. The types of two
      //   non-static member functions are considered to be different, for the
      //   purposes of substitution, if the functions are members of different
      //   classes. In other words, for the purposes of substitution, the class of
      //   which the function is a member is considered part of the type of
      //   function.
  
      // Given that we already substitute member function pointers as a
      // whole, the net effect of this rule is just to unconditionally
      // suppress substitution on the function type in a member pointer.
      // We increment the SeqID here to emulate adding an entry to the
      // substitution table.
      ++SeqID;
    } else
      mangleType(PointeeType);
  }
  
  // <type>           ::= <template-param>
  void CXXNameMangler::mangleType(const TemplateTypeParmType *T) {
    mangleTemplateParameter(T->getDepth(), T->getIndex());
  }
  
  // <type>           ::= <template-param>
  void CXXNameMangler::mangleType(const SubstTemplateTypeParmPackType *T) {
    // FIXME: not clear how to mangle this!
    // template <class T...> class A {
    //   template <class U...> void foo(T(*)(U) x...);
    // };
    Out << "_SUBSTPACK_";
  }
  
  // <type> ::= P <type>   # pointer-to
  void CXXNameMangler::mangleType(const PointerType *T) {
    Out << 'P';
    mangleType(T->getPointeeType());
  }
  void CXXNameMangler::mangleType(const ObjCObjectPointerType *T) {
    Out << 'P';
    mangleType(T->getPointeeType());
  }
  
  // <type> ::= R <type>   # reference-to
  void CXXNameMangler::mangleType(const LValueReferenceType *T) {
    Out << 'R';
    mangleType(T->getPointeeType());
  }
  
  // <type> ::= O <type>   # rvalue reference-to (C++0x)
  void CXXNameMangler::mangleType(const RValueReferenceType *T) {
    Out << 'O';
    mangleType(T->getPointeeType());
  }
  
  // <type> ::= C <type>   # complex pair (C 2000)
  void CXXNameMangler::mangleType(const ComplexType *T) {
    Out << 'C';
    mangleType(T->getElementType());
  }
  
  // ARM's ABI for Neon vector types specifies that they should be mangled as
  // if they are structs (to match ARM's initial implementation).  The
  // vector type must be one of the special types predefined by ARM.
  void CXXNameMangler::mangleNeonVectorType(const VectorType *T) {
    QualType EltType = T->getElementType();
    assert(EltType->isBuiltinType() && "Neon vector element not a BuiltinType");
    const char *EltName = nullptr;
    if (T->getVectorKind() == VectorType::NeonPolyVector) {
      switch (cast<BuiltinType>(EltType)->getKind()) {
      case BuiltinType::SChar:
      case BuiltinType::UChar:
        EltName = "poly8_t";
        break;
      case BuiltinType::Short:
      case BuiltinType::UShort:
        EltName = "poly16_t";
        break;
      case BuiltinType::LongLong:
      case BuiltinType::ULongLong:
        EltName = "poly64_t";
        break;
      default: llvm_unreachable("unexpected Neon polynomial vector element type");
      }
    } else {
      switch (cast<BuiltinType>(EltType)->getKind()) {
      case BuiltinType::SChar:     EltName = "int8_t"; break;
      case BuiltinType::UChar:     EltName = "uint8_t"; break;
      case BuiltinType::Short:     EltName = "int16_t"; break;
      case BuiltinType::UShort:    EltName = "uint16_t"; break;
      case BuiltinType::Int:       EltName = "int32_t"; break;
      case BuiltinType::UInt:      EltName = "uint32_t"; break;
      case BuiltinType::LongLong:  EltName = "int64_t"; break;
      case BuiltinType::ULongLong: EltName = "uint64_t"; break;
      case BuiltinType::Double:    EltName = "float64_t"; break;
      case BuiltinType::Float:     EltName = "float32_t"; break;
      case BuiltinType::Half:      EltName = "float16_t"; break;
      case BuiltinType::BFloat16:  EltName = "bfloat16_t"; break;
      default:
        llvm_unreachable("unexpected Neon vector element type");
      }
    }
    const char *BaseName = nullptr;
    unsigned BitSize = (T->getNumElements() *
                        getASTContext().getTypeSize(EltType));
    if (BitSize == 64)
      BaseName = "__simd64_";
    else {
      assert(BitSize == 128 && "Neon vector type not 64 or 128 bits");
      BaseName = "__simd128_";
    }
    Out << strlen(BaseName) + strlen(EltName);
    Out << BaseName << EltName;
  }
  
  void CXXNameMangler::mangleNeonVectorType(const DependentVectorType *T) {
    DiagnosticsEngine &Diags = Context.getDiags();
    unsigned DiagID = Diags.getCustomDiagID(
        DiagnosticsEngine::Error,
        "cannot mangle this dependent neon vector type yet");
    Diags.Report(T->getAttributeLoc(), DiagID);
  }
  
  static StringRef mangleAArch64VectorBase(const BuiltinType *EltType) {
    switch (EltType->getKind()) {
    case BuiltinType::SChar:
      return "Int8";
    case BuiltinType::Short:
      return "Int16";
    case BuiltinType::Int:
      return "Int32";
    case BuiltinType::Long:
    case BuiltinType::LongLong:
      return "Int64";
    case BuiltinType::UChar:
      return "Uint8";
    case BuiltinType::UShort:
      return "Uint16";
    case BuiltinType::UInt:
      return "Uint32";
    case BuiltinType::ULong:
    case BuiltinType::ULongLong:
      return "Uint64";
    case BuiltinType::Half:
      return "Float16";
    case BuiltinType::Float:
      return "Float32";
    case BuiltinType::Double:
      return "Float64";
    case BuiltinType::BFloat16:
      return "Bfloat16";
    default:
      llvm_unreachable("Unexpected vector element base type");
    }
  }
  
  // AArch64's ABI for Neon vector types specifies that they should be mangled as
  // the equivalent internal name. The vector type must be one of the special
  // types predefined by ARM.
  void CXXNameMangler::mangleAArch64NeonVectorType(const VectorType *T) {
    QualType EltType = T->getElementType();
    assert(EltType->isBuiltinType() && "Neon vector element not a BuiltinType");
    unsigned BitSize =
        (T->getNumElements() * getASTContext().getTypeSize(EltType));
    (void)BitSize; // Silence warning.
  
    assert((BitSize == 64 || BitSize == 128) &&
           "Neon vector type not 64 or 128 bits");
  
    StringRef EltName;
    if (T->getVectorKind() == VectorType::NeonPolyVector) {
      switch (cast<BuiltinType>(EltType)->getKind()) {
      case BuiltinType::UChar:
        EltName = "Poly8";
        break;
      case BuiltinType::UShort:
        EltName = "Poly16";
        break;
      case BuiltinType::ULong:
      case BuiltinType::ULongLong:
        EltName = "Poly64";
        break;
      default:
        llvm_unreachable("unexpected Neon polynomial vector element type");
      }
    } else
      EltName = mangleAArch64VectorBase(cast<BuiltinType>(EltType));
  
    std::string TypeName =
        ("__" + EltName + "x" + Twine(T->getNumElements()) + "_t").str();
    Out << TypeName.length() << TypeName;
  }
  void CXXNameMangler::mangleAArch64NeonVectorType(const DependentVectorType *T) {
    DiagnosticsEngine &Diags = Context.getDiags();
    unsigned DiagID = Diags.getCustomDiagID(
        DiagnosticsEngine::Error,
        "cannot mangle this dependent neon vector type yet");
    Diags.Report(T->getAttributeLoc(), DiagID);
  }
  
  // The AArch64 ACLE specifies that fixed-length SVE vector and predicate types
  // defined with the 'arm_sve_vector_bits' attribute map to the same AAPCS64
  // type as the sizeless variants.
  //
  // The mangling scheme for VLS types is implemented as a "pseudo" template:
  //
  //   '__SVE_VLS<<type>, <vector length>>'
  //
  // Combining the existing SVE type and a specific vector length (in bits).
  // For example:
  //
  //   typedef __SVInt32_t foo __attribute__((arm_sve_vector_bits(512)));
  //
  // is described as '__SVE_VLS<__SVInt32_t, 512u>' and mangled as:
  //
  //   "9__SVE_VLSI" + base type mangling + "Lj" + __ARM_FEATURE_SVE_BITS + "EE"
  //
  //   i.e. 9__SVE_VLSIu11__SVInt32_tLj512EE
  //
  // The latest ACLE specification (00bet5) does not contain details of this
  // mangling scheme, it will be specified in the next revision. The mangling
  // scheme is otherwise defined in the appendices to the Procedure Call Standard
  // for the Arm Architecture, see
  // https://github.com/ARM-software/abi-aa/blob/master/aapcs64/aapcs64.rst#appendix-c-mangling
  void CXXNameMangler::mangleAArch64FixedSveVectorType(const VectorType *T) {
    assert((T->getVectorKind() == VectorType::SveFixedLengthDataVector ||
            T->getVectorKind() == VectorType::SveFixedLengthPredicateVector) &&
           "expected fixed-length SVE vector!");
  
    QualType EltType = T->getElementType();
    assert(EltType->isBuiltinType() &&
           "expected builtin type for fixed-length SVE vector!");
  
    StringRef TypeName;
    switch (cast<BuiltinType>(EltType)->getKind()) {
    case BuiltinType::SChar:
      TypeName = "__SVInt8_t";
      break;
    case BuiltinType::UChar: {
      if (T->getVectorKind() == VectorType::SveFixedLengthDataVector)
        TypeName = "__SVUint8_t";
      else
        TypeName = "__SVBool_t";
      break;
    }
    case BuiltinType::Short:
      TypeName = "__SVInt16_t";
      break;
    case BuiltinType::UShort:
      TypeName = "__SVUint16_t";
      break;
    case BuiltinType::Int:
      TypeName = "__SVInt32_t";
      break;
    case BuiltinType::UInt:
      TypeName = "__SVUint32_t";
      break;
    case BuiltinType::Long:
      TypeName = "__SVInt64_t";
      break;
    case BuiltinType::ULong:
      TypeName = "__SVUint64_t";
      break;
    case BuiltinType::Half:
      TypeName = "__SVFloat16_t";
      break;
    case BuiltinType::Float:
      TypeName = "__SVFloat32_t";
      break;
    case BuiltinType::Double:
      TypeName = "__SVFloat64_t";
      break;
    case BuiltinType::BFloat16:
      TypeName = "__SVBfloat16_t";
      break;
    default:
      llvm_unreachable("unexpected element type for fixed-length SVE vector!");
    }
  
    unsigned VecSizeInBits = getASTContext().getTypeInfo(T).Width;
  
    if (T->getVectorKind() == VectorType::SveFixedLengthPredicateVector)
      VecSizeInBits *= 8;
  
    Out << "9__SVE_VLSI" << 'u' << TypeName.size() << TypeName << "Lj"
        << VecSizeInBits << "EE";
  }
  
  void CXXNameMangler::mangleAArch64FixedSveVectorType(
      const DependentVectorType *T) {
    DiagnosticsEngine &Diags = Context.getDiags();
    unsigned DiagID = Diags.getCustomDiagID(
        DiagnosticsEngine::Error,
        "cannot mangle this dependent fixed-length SVE vector type yet");
    Diags.Report(T->getAttributeLoc(), DiagID);
  }
  
  // GNU extension: vector types
  // <type>                  ::= <vector-type>
  // <vector-type>           ::= Dv <positive dimension number> _
  //                                    <extended element type>
  //                         ::= Dv [<dimension expression>] _ <element type>
  // <extended element type> ::= <element type>
  //                         ::= p # AltiVec vector pixel
  //                         ::= b # Altivec vector bool
  void CXXNameMangler::mangleType(const VectorType *T) {
    if ((T->getVectorKind() == VectorType::NeonVector ||
         T->getVectorKind() == VectorType::NeonPolyVector)) {
      llvm::Triple Target = getASTContext().getTargetInfo().getTriple();
      llvm::Triple::ArchType Arch =
          getASTContext().getTargetInfo().getTriple().getArch();
      if ((Arch == llvm::Triple::aarch64 ||
           Arch == llvm::Triple::aarch64_be) && !Target.isOSDarwin())
        mangleAArch64NeonVectorType(T);
      else
        mangleNeonVectorType(T);
      return;
    } else if (T->getVectorKind() == VectorType::SveFixedLengthDataVector ||
               T->getVectorKind() == VectorType::SveFixedLengthPredicateVector) {
      mangleAArch64FixedSveVectorType(T);
      return;
    }
    Out << "Dv" << T->getNumElements() << '_';
    if (T->getVectorKind() == VectorType::AltiVecPixel)
      Out << 'p';
    else if (T->getVectorKind() == VectorType::AltiVecBool)
      Out << 'b';
    else
      mangleType(T->getElementType());
  }
  
  void CXXNameMangler::mangleType(const DependentVectorType *T) {
    if ((T->getVectorKind() == VectorType::NeonVector ||
         T->getVectorKind() == VectorType::NeonPolyVector)) {
      llvm::Triple Target = getASTContext().getTargetInfo().getTriple();
      llvm::Triple::ArchType Arch =
          getASTContext().getTargetInfo().getTriple().getArch();
      if ((Arch == llvm::Triple::aarch64 || Arch == llvm::Triple::aarch64_be) &&
          !Target.isOSDarwin())
        mangleAArch64NeonVectorType(T);
      else
        mangleNeonVectorType(T);
      return;
    } else if (T->getVectorKind() == VectorType::SveFixedLengthDataVector ||
               T->getVectorKind() == VectorType::SveFixedLengthPredicateVector) {
      mangleAArch64FixedSveVectorType(T);
      return;
    }
  
    Out << "Dv";
    mangleExpression(T->getSizeExpr());
    Out << '_';
    if (T->getVectorKind() == VectorType::AltiVecPixel)
      Out << 'p';
    else if (T->getVectorKind() == VectorType::AltiVecBool)
      Out << 'b';
    else
      mangleType(T->getElementType());
  }
  
  void CXXNameMangler::mangleType(const ExtVectorType *T) {
    mangleType(static_cast<const VectorType*>(T));
  }
  void CXXNameMangler::mangleType(const DependentSizedExtVectorType *T) {
    Out << "Dv";
    mangleExpression(T->getSizeExpr());
    Out << '_';
    mangleType(T->getElementType());
  }
  
  void CXXNameMangler::mangleType(const ConstantMatrixType *T) {
    // Mangle matrix types using a vendor extended type qualifier:
    // U<Len>matrix_type<Rows><Columns><element type>
    StringRef VendorQualifier = "matrix_type";
    Out << "U" << VendorQualifier.size() << VendorQualifier;
    auto &ASTCtx = getASTContext();
    unsigned BitWidth = ASTCtx.getTypeSize(ASTCtx.getSizeType());
    llvm::APSInt Rows(BitWidth);
    Rows = T->getNumRows();
    mangleIntegerLiteral(ASTCtx.getSizeType(), Rows);
    llvm::APSInt Columns(BitWidth);
    Columns = T->getNumColumns();
    mangleIntegerLiteral(ASTCtx.getSizeType(), Columns);
    mangleType(T->getElementType());
  }
  
  void CXXNameMangler::mangleType(const DependentSizedMatrixType *T) {
    // U<Len>matrix_type<row expr><column expr><element type>
    StringRef VendorQualifier = "matrix_type";
    Out << "U" << VendorQualifier.size() << VendorQualifier;
    mangleTemplateArg(T->getRowExpr());
    mangleTemplateArg(T->getColumnExpr());
    mangleType(T->getElementType());
  }
  
  void CXXNameMangler::mangleType(const DependentAddressSpaceType *T) {
    SplitQualType split = T->getPointeeType().split();
    mangleQualifiers(split.Quals, T);
    mangleType(QualType(split.Ty, 0));
  }
  
  void CXXNameMangler::mangleType(const PackExpansionType *T) {
    // <type>  ::= Dp <type>          # pack expansion (C++0x)
    Out << "Dp";
    mangleType(T->getPattern());
  }
  
  void CXXNameMangler::mangleType(const ObjCInterfaceType *T) {
    mangleSourceName(T->getDecl()->getIdentifier());
  }
  
  void CXXNameMangler::mangleType(const ObjCObjectType *T) {
    // Treat __kindof as a vendor extended type qualifier.
    if (T->isKindOfType())
      Out << "U8__kindof";
  
    if (!T->qual_empty()) {
      // Mangle protocol qualifiers.
      SmallString<64> QualStr;
      llvm::raw_svector_ostream QualOS(QualStr);
      QualOS << "objcproto";
      for (const auto *I : T->quals()) {
        StringRef name = I->getName();
        QualOS << name.size() << name;
      }
      Out << 'U' << QualStr.size() << QualStr;
    }
  
    mangleType(T->getBaseType());
  
    if (T->isSpecialized()) {
      // Mangle type arguments as I <type>+ E
      Out << 'I';
      for (auto typeArg : T->getTypeArgs())
        mangleType(typeArg);
      Out << 'E';
    }
  }
  
  void CXXNameMangler::mangleType(const BlockPointerType *T) {
    Out << "U13block_pointer";
    mangleType(T->getPointeeType());
  }
  
  void CXXNameMangler::mangleType(const InjectedClassNameType *T) {
    // Mangle injected class name types as if the user had written the
    // specialization out fully.  It may not actually be possible to see
    // this mangling, though.
    mangleType(T->getInjectedSpecializationType());
  }
  
  void CXXNameMangler::mangleType(const TemplateSpecializationType *T) {
    if (TemplateDecl *TD = T->getTemplateName().getAsTemplateDecl()) {
      mangleTemplateName(TD, T->getArgs(), T->getNumArgs());
    } else {
      if (mangleSubstitution(QualType(T, 0)))
        return;
  
      mangleTemplatePrefix(T->getTemplateName());
  
      // FIXME: GCC does not appear to mangle the template arguments when
      // the template in question is a dependent template name. Should we
      // emulate that badness?
      mangleTemplateArgs(T->getArgs(), T->getNumArgs());
      addSubstitution(QualType(T, 0));
    }
  }
  
  void CXXNameMangler::mangleType(const DependentNameType *T) {
    // Proposal by cxx-abi-dev, 2014-03-26
    // <class-enum-type> ::= <name>    # non-dependent or dependent type name or
    //                                 # dependent elaborated type specifier using
    //                                 # 'typename'
    //                   ::= Ts <name> # dependent elaborated type specifier using
    //                                 # 'struct' or 'class'
    //                   ::= Tu <name> # dependent elaborated type specifier using
    //                                 # 'union'
    //                   ::= Te <name> # dependent elaborated type specifier using
    //                                 # 'enum'
    switch (T->getKeyword()) {
      case ETK_None:
      case ETK_Typename:
        break;
      case ETK_Struct:
      case ETK_Class:
      case ETK_Interface:
        Out << "Ts";
        break;
      case ETK_Union:
        Out << "Tu";
        break;
      case ETK_Enum:
        Out << "Te";
        break;
    }
    // Typename types are always nested
    Out << 'N';
    manglePrefix(T->getQualifier());
    mangleSourceName(T->getIdentifier());
    Out << 'E';
  }
  
  void CXXNameMangler::mangleType(const DependentTemplateSpecializationType *T) {
    // Dependently-scoped template types are nested if they have a prefix.
    Out << 'N';
  
    // TODO: avoid making this TemplateName.
    TemplateName Prefix =
      getASTContext().getDependentTemplateName(T->getQualifier(),
                                               T->getIdentifier());
    mangleTemplatePrefix(Prefix);
  
    // FIXME: GCC does not appear to mangle the template arguments when
    // the template in question is a dependent template name. Should we
    // emulate that badness?
    mangleTemplateArgs(T->getArgs(), T->getNumArgs());
    Out << 'E';
  }
  
  void CXXNameMangler::mangleType(const TypeOfType *T) {
    // FIXME: this is pretty unsatisfactory, but there isn't an obvious
    // "extension with parameters" mangling.
    Out << "u6typeof";
  }
  
  void CXXNameMangler::mangleType(const TypeOfExprType *T) {
    // FIXME: this is pretty unsatisfactory, but there isn't an obvious
    // "extension with parameters" mangling.
    Out << "u6typeof";
  }
  
  void CXXNameMangler::mangleType(const DecltypeType *T) {
    Expr *E = T->getUnderlyingExpr();
  
    // type ::= Dt <expression> E  # decltype of an id-expression
    //                             #   or class member access
    //      ::= DT <expression> E  # decltype of an expression
  
    // This purports to be an exhaustive list of id-expressions and
    // class member accesses.  Note that we do not ignore parentheses;
    // parentheses change the semantics of decltype for these
    // expressions (and cause the mangler to use the other form).
    if (isa<DeclRefExpr>(E) ||
        isa<MemberExpr>(E) ||
        isa<UnresolvedLookupExpr>(E) ||
        isa<DependentScopeDeclRefExpr>(E) ||
        isa<CXXDependentScopeMemberExpr>(E) ||
        isa<UnresolvedMemberExpr>(E))
      Out << "Dt";
    else
      Out << "DT";
    mangleExpression(E);
    Out << 'E';
  }
  
  void CXXNameMangler::mangleType(const UnaryTransformType *T) {
    // If this is dependent, we need to record that. If not, we simply
    // mangle it as the underlying type since they are equivalent.
    if (T->isDependentType()) {
      Out << 'U';
  
      switch (T->getUTTKind()) {
        case UnaryTransformType::EnumUnderlyingType:
          Out << "3eut";
          break;
      }
    }
  
    mangleType(T->getBaseType());
  }
  
  void CXXNameMangler::mangleType(const AutoType *T) {
    assert(T->getDeducedType().isNull() &&
           "Deduced AutoType shouldn't be handled here!");
    assert(T->getKeyword() != AutoTypeKeyword::GNUAutoType &&
           "shouldn't need to mangle __auto_type!");
    // <builtin-type> ::= Da # auto
    //                ::= Dc # decltype(auto)
    Out << (T->isDecltypeAuto() ? "Dc" : "Da");
  }
  
  void CXXNameMangler::mangleType(const DeducedTemplateSpecializationType *T) {
    QualType Deduced = T->getDeducedType();
    if (!Deduced.isNull())
      mangleType(Deduced);
    else if (TemplateDecl *TD = T->getTemplateName().getAsTemplateDecl())
      mangleName(GlobalDecl(TD));
    else {
      // For an unresolved template-name, mangle it as if it were a template
      // specialization but leave off the template arguments.
      Out << 'N';
      mangleTemplatePrefix(T->getTemplateName());
      Out << 'E';
    }
  }
  
  void CXXNameMangler::mangleType(const AtomicType *T) {
    // <type> ::= U <source-name> <type>  # vendor extended type qualifier
    // (Until there's a standardized mangling...)
    Out << "U7_Atomic";
    mangleType(T->getValueType());
  }
  
  void CXXNameMangler::mangleType(const PipeType *T) {
    // Pipe type mangling rules are described in SPIR 2.0 specification
    // A.1 Data types and A.3 Summary of changes
    // <type> ::= 8ocl_pipe
    Out << "8ocl_pipe";
  }
  
  void CXXNameMangler::mangleType(const ExtIntType *T) {
    Out << "U7_ExtInt";
    llvm::APSInt BW(32, true);
    BW = T->getNumBits();
    TemplateArgument TA(Context.getASTContext(), BW, getASTContext().IntTy);
    mangleTemplateArgs(&TA, 1);
    if (T->isUnsigned())
      Out << "j";
    else
      Out << "i";
  }
  
  void CXXNameMangler::mangleType(const DependentExtIntType *T) {
    Out << "U7_ExtInt";
    TemplateArgument TA(T->getNumBitsExpr());
    mangleTemplateArgs(&TA, 1);
    if (T->isUnsigned())
      Out << "j";
    else
      Out << "i";
  }
  
  void CXXNameMangler::mangleIntegerLiteral(QualType T,
                                            const llvm::APSInt &Value) {
    //  <expr-primary> ::= L <type> <value number> E # integer literal
    Out << 'L';
  
    mangleType(T);
    if (T->isBooleanType()) {
      // Boolean values are encoded as 0/1.
      Out << (Value.getBoolValue() ? '1' : '0');
    } else {
      mangleNumber(Value);
    }
    Out << 'E';
  
  }
  
  void CXXNameMangler::mangleMemberExprBase(const Expr *Base, bool IsArrow) {
    // Ignore member expressions involving anonymous unions.
    while (const auto *RT = Base->getType()->getAs<RecordType>()) {
      if (!RT->getDecl()->isAnonymousStructOrUnion())
        break;
      const auto *ME = dyn_cast<MemberExpr>(Base);
      if (!ME)
        break;
      Base = ME->getBase();
      IsArrow = ME->isArrow();
    }
  
    if (Base->isImplicitCXXThis()) {
      // Note: GCC mangles member expressions to the implicit 'this' as
      // *this., whereas we represent them as this->. The Itanium C++ ABI
      // does not specify anything here, so we follow GCC.
      Out << "dtdefpT";
    } else {
      Out << (IsArrow ? "pt" : "dt");
      mangleExpression(Base);
    }
  }
  
  /// Mangles a member expression.
  void CXXNameMangler::mangleMemberExpr(const Expr *base,
                                        bool isArrow,
                                        NestedNameSpecifier *qualifier,
                                        NamedDecl *firstQualifierLookup,
                                        DeclarationName member,
                                        const TemplateArgumentLoc *TemplateArgs,
                                        unsigned NumTemplateArgs,
                                        unsigned arity) {
    // <expression> ::= dt <expression> <unresolved-name>
    //              ::= pt <expression> <unresolved-name>
    if (base)
      mangleMemberExprBase(base, isArrow);
    mangleUnresolvedName(qualifier, member, TemplateArgs, NumTemplateArgs, arity);
  }
  
  /// Look at the callee of the given call expression and determine if
  /// it's a parenthesized id-expression which would have triggered ADL
  /// otherwise.
  static bool isParenthesizedADLCallee(const CallExpr *call) {
    const Expr *callee = call->getCallee();
    const Expr *fn = callee->IgnoreParens();
  
    // Must be parenthesized.  IgnoreParens() skips __extension__ nodes,
    // too, but for those to appear in the callee, it would have to be
    // parenthesized.
    if (callee == fn) return false;
  
    // Must be an unresolved lookup.
    const UnresolvedLookupExpr *lookup = dyn_cast<UnresolvedLookupExpr>(fn);
    if (!lookup) return false;
  
    assert(!lookup->requiresADL());
  
    // Must be an unqualified lookup.
    if (lookup->getQualifier()) return false;
  
    // Must not have found a class member.  Note that if one is a class
    // member, they're all class members.
    if (lookup->getNumDecls() > 0 &&
        (*lookup->decls_begin())->isCXXClassMember())
      return false;
  
    // Otherwise, ADL would have been triggered.
    return true;
  }
  
  void CXXNameMangler::mangleCastExpression(const Expr *E, StringRef CastEncoding) {
    const ExplicitCastExpr *ECE = cast<ExplicitCastExpr>(E);
    Out << CastEncoding;
    mangleType(ECE->getType());
    mangleExpression(ECE->getSubExpr());
  }
  
  void CXXNameMangler::mangleInitListElements(const InitListExpr *InitList) {
    if (auto *Syntactic = InitList->getSyntacticForm())
      InitList = Syntactic;
    for (unsigned i = 0, e = InitList->getNumInits(); i != e; ++i)
      mangleExpression(InitList->getInit(i));
  }
  
  void CXXNameMangler::mangleDeclRefExpr(const NamedDecl *D) {
    switch (D->getKind()) {
    default:
      //  <expr-primary> ::= L <mangled-name> E # external name
      Out << 'L';
      mangle(D);
      Out << 'E';
      break;
  
    case Decl::ParmVar:
      mangleFunctionParam(cast<ParmVarDecl>(D));
      break;
  
    case Decl::EnumConstant: {
      const EnumConstantDecl *ED = cast<EnumConstantDecl>(D);
      mangleIntegerLiteral(ED->getType(), ED->getInitVal());
      break;
    }
  
    case Decl::NonTypeTemplateParm:
      const NonTypeTemplateParmDecl *PD = cast<NonTypeTemplateParmDecl>(D);
      mangleTemplateParameter(PD->getDepth(), PD->getIndex());
      break;
    }
  }
  
  void CXXNameMangler::mangleExpression(const Expr *E, unsigned Arity) {
    // <expression> ::= <unary operator-name> <expression>
    //              ::= <binary operator-name> <expression> <expression>
    //              ::= <trinary operator-name> <expression> <expression> <expression>
    //              ::= cv <type> expression           # conversion with one argument
    //              ::= cv <type> _ <expression>* E # conversion with a different number of arguments
    //              ::= dc <type> <expression>         # dynamic_cast<type> (expression)
    //              ::= sc <type> <expression>         # static_cast<type> (expression)
    //              ::= cc <type> <expression>         # const_cast<type> (expression)
    //              ::= rc <type> <expression>         # reinterpret_cast<type> (expression)
    //              ::= st <type>                      # sizeof (a type)
    //              ::= at <type>                      # alignof (a type)
    //              ::= <template-param>
    //              ::= <function-param>
    //              ::= sr <type> <unqualified-name>                   # dependent name
    //              ::= sr <type> <unqualified-name> <template-args>   # dependent template-id
    //              ::= ds <expression> <expression>                   # expr.*expr
    //              ::= sZ <template-param>                            # size of a parameter pack
    //              ::= sZ <function-param>    # size of a function parameter pack
    //              ::= <expr-primary>
    // <expr-primary> ::= L <type> <value number> E    # integer literal
    //                ::= L <type <value float> E      # floating literal
    //                ::= L <mangled-name> E           # external name
    //                ::= fpT                          # 'this' expression
    QualType ImplicitlyConvertedToType;
  
  recurse:
    switch (E->getStmtClass()) {
    case Expr::NoStmtClass:
  #define ABSTRACT_STMT(Type)
  #define EXPR(Type, Base)
  #define STMT(Type, Base) \
    case Expr::Type##Class:
  #include "clang/AST/StmtNodes.inc"
      // fallthrough
  
    // These all can only appear in local or variable-initialization
    // contexts and so should never appear in a mangling.
    case Expr::AddrLabelExprClass:
    case Expr::DesignatedInitUpdateExprClass:
    case Expr::ImplicitValueInitExprClass:
    case Expr::ArrayInitLoopExprClass:
    case Expr::ArrayInitIndexExprClass:
    case Expr::NoInitExprClass:
    case Expr::ParenListExprClass:
    case Expr::LambdaExprClass:
    case Expr::MSPropertyRefExprClass:
    case Expr::MSPropertySubscriptExprClass:
    case Expr::TypoExprClass: // This should no longer exist in the AST by now.
    case Expr::RecoveryExprClass:
    case Expr::OMPArraySectionExprClass:
    case Expr::OMPArrayShapingExprClass:
    case Expr::OMPIteratorExprClass:
    case Expr::CXXInheritedCtorInitExprClass:
      llvm_unreachable("unexpected statement kind");
  
    case Expr::ConstantExprClass:
      E = cast<ConstantExpr>(E)->getSubExpr();
      goto recurse;
  
    // FIXME: invent manglings for all these.
    case Expr::BlockExprClass:
    case Expr::ChooseExprClass:
    case Expr::CompoundLiteralExprClass:
    case Expr::ExtVectorElementExprClass:
    case Expr::GenericSelectionExprClass:
    case Expr::ObjCEncodeExprClass:
    case Expr::ObjCIsaExprClass:
    case Expr::ObjCIvarRefExprClass:
    case Expr::ObjCMessageExprClass:
    case Expr::ObjCPropertyRefExprClass:
    case Expr::ObjCProtocolExprClass:
    case Expr::ObjCSelectorExprClass:
    case Expr::ObjCStringLiteralClass:
    case Expr::ObjCBoxedExprClass:
    case Expr::ObjCArrayLiteralClass:
    case Expr::ObjCDictionaryLiteralClass:
    case Expr::ObjCSubscriptRefExprClass:
    case Expr::ObjCIndirectCopyRestoreExprClass:
    case Expr::ObjCAvailabilityCheckExprClass:
    case Expr::OffsetOfExprClass:
    case Expr::PredefinedExprClass:
    case Expr::ShuffleVectorExprClass:
    case Expr::ConvertVectorExprClass:
    case Expr::StmtExprClass:
    case Expr::TypeTraitExprClass:
    case Expr::RequiresExprClass:
    case Expr::ArrayTypeTraitExprClass:
    case Expr::ExpressionTraitExprClass:
    case Expr::VAArgExprClass:
    case Expr::CUDAKernelCallExprClass:
    case Expr::AsTypeExprClass:
    case Expr::PseudoObjectExprClass:
    case Expr::AtomicExprClass:
    case Expr::SourceLocExprClass:
    case Expr::FixedPointLiteralClass:
    case Expr::BuiltinBitCastExprClass:
    {
      if (!NullOut) {
        // As bad as this diagnostic is, it's better than crashing.
        DiagnosticsEngine &Diags = Context.getDiags();
        unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
                                         "cannot yet mangle expression type %0");
        Diags.Report(E->getExprLoc(), DiagID)
          << E->getStmtClassName() << E->getSourceRange();
      }
      break;
    }
  
    case Expr::CXXUuidofExprClass: {
      const CXXUuidofExpr *UE = cast<CXXUuidofExpr>(E);
      if (UE->isTypeOperand()) {
        QualType UuidT = UE->getTypeOperand(Context.getASTContext());
        Out << "u8__uuidoft";
        mangleType(UuidT);
      } else {
        Expr *UuidExp = UE->getExprOperand();
        Out << "u8__uuidofz";
        mangleExpression(UuidExp, Arity);
      }
      break;
    }
  
    // Even gcc-4.5 doesn't mangle this.
    case Expr::BinaryConditionalOperatorClass: {
      DiagnosticsEngine &Diags = Context.getDiags();
      unsigned DiagID =
        Diags.getCustomDiagID(DiagnosticsEngine::Error,
                  "?: operator with omitted middle operand cannot be mangled");
      Diags.Report(E->getExprLoc(), DiagID)
        << E->getStmtClassName() << E->getSourceRange();
      break;
    }
  
    // These are used for internal purposes and cannot be meaningfully mangled.
    case Expr::OpaqueValueExprClass:
      llvm_unreachable("cannot mangle opaque value; mangling wrong thing?");
  
    case Expr::InitListExprClass: {
      Out << "il";
      mangleInitListElements(cast<InitListExpr>(E));
      Out << "E";
      break;
    }
  
    case Expr::DesignatedInitExprClass: {
      auto *DIE = cast<DesignatedInitExpr>(E);
      for (const auto &Designator : DIE->designators()) {
        if (Designator.isFieldDesignator()) {
          Out << "di";
          mangleSourceName(Designator.getFieldName());
        } else if (Designator.isArrayDesignator()) {
          Out << "dx";
          mangleExpression(DIE->getArrayIndex(Designator));
        } else {
          assert(Designator.isArrayRangeDesignator() &&
                 "unknown designator kind");
          Out << "dX";
          mangleExpression(DIE->getArrayRangeStart(Designator));
          mangleExpression(DIE->getArrayRangeEnd(Designator));
        }
      }
      mangleExpression(DIE->getInit());
      break;
    }
  
    case Expr::CXXDefaultArgExprClass:
      mangleExpression(cast<CXXDefaultArgExpr>(E)->getExpr(), Arity);
      break;
  
    case Expr::CXXDefaultInitExprClass:
      mangleExpression(cast<CXXDefaultInitExpr>(E)->getExpr(), Arity);
      break;
  
    case Expr::CXXStdInitializerListExprClass:
      mangleExpression(cast<CXXStdInitializerListExpr>(E)->getSubExpr(), Arity);
      break;
  
    case Expr::SubstNonTypeTemplateParmExprClass:
      mangleExpression(cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement(),
                       Arity);
      break;
  
    case Expr::UserDefinedLiteralClass:
      // We follow g++'s approach of mangling a UDL as a call to the literal
      // operator.
    case Expr::CXXMemberCallExprClass: // fallthrough
    case Expr::CallExprClass: {
      const CallExpr *CE = cast<CallExpr>(E);
  
      // <expression> ::= cp <simple-id> <expression>* E
      // We use this mangling only when the call would use ADL except
      // for being parenthesized.  Per discussion with David
      // Vandervoorde, 2011.04.25.
      if (isParenthesizedADLCallee(CE)) {
        Out << "cp";
        // The callee here is a parenthesized UnresolvedLookupExpr with
        // no qualifier and should always get mangled as a <simple-id>
        // anyway.
  
      // <expression> ::= cl <expression>* E
      } else {
        Out << "cl";
      }
  
      unsigned CallArity = CE->getNumArgs();
      for (const Expr *Arg : CE->arguments())
        if (isa<PackExpansionExpr>(Arg))
          CallArity = UnknownArity;
  
      mangleExpression(CE->getCallee(), CallArity);
      for (const Expr *Arg : CE->arguments())
        mangleExpression(Arg);
      Out << 'E';
      break;
    }
  
    case Expr::CXXNewExprClass: {
      const CXXNewExpr *New = cast<CXXNewExpr>(E);
      if (New->isGlobalNew()) Out << "gs";
      Out << (New->isArray() ? "na" : "nw");
      for (CXXNewExpr::const_arg_iterator I = New->placement_arg_begin(),
             E = New->placement_arg_end(); I != E; ++I)
        mangleExpression(*I);
      Out << '_';
      mangleType(New->getAllocatedType());
      if (New->hasInitializer()) {
        if (New->getInitializationStyle() == CXXNewExpr::ListInit)
          Out << "il";
        else
          Out << "pi";
        const Expr *Init = New->getInitializer();
        if (const CXXConstructExpr *CCE = dyn_cast<CXXConstructExpr>(Init)) {
          // Directly inline the initializers.
          for (CXXConstructExpr::const_arg_iterator I = CCE->arg_begin(),
                                                    E = CCE->arg_end();
               I != E; ++I)
            mangleExpression(*I);
        } else if (const ParenListExpr *PLE = dyn_cast<ParenListExpr>(Init)) {
          for (unsigned i = 0, e = PLE->getNumExprs(); i != e; ++i)
            mangleExpression(PLE->getExpr(i));
        } else if (New->getInitializationStyle() == CXXNewExpr::ListInit &&
                   isa<InitListExpr>(Init)) {
          // Only take InitListExprs apart for list-initialization.
          mangleInitListElements(cast<InitListExpr>(Init));
        } else
          mangleExpression(Init);
      }
      Out << 'E';
      break;
    }
  
    case Expr::CXXPseudoDestructorExprClass: {
      const auto *PDE = cast<CXXPseudoDestructorExpr>(E);
      if (const Expr *Base = PDE->getBase())
        mangleMemberExprBase(Base, PDE->isArrow());
      NestedNameSpecifier *Qualifier = PDE->getQualifier();
      if (TypeSourceInfo *ScopeInfo = PDE->getScopeTypeInfo()) {
        if (Qualifier) {
          mangleUnresolvedPrefix(Qualifier,
                                 /*recursive=*/true);
          mangleUnresolvedTypeOrSimpleId(ScopeInfo->getType());
          Out << 'E';
        } else {
          Out << "sr";
          if (!mangleUnresolvedTypeOrSimpleId(ScopeInfo->getType()))
            Out << 'E';
        }
      } else if (Qualifier) {
        mangleUnresolvedPrefix(Qualifier);
      }
      // <base-unresolved-name> ::= dn <destructor-name>
      Out << "dn";
      QualType DestroyedType = PDE->getDestroyedType();
      mangleUnresolvedTypeOrSimpleId(DestroyedType);
      break;
    }
  
    case Expr::MemberExprClass: {
      const MemberExpr *ME = cast<MemberExpr>(E);
      mangleMemberExpr(ME->getBase(), ME->isArrow(),
                       ME->getQualifier(), nullptr,
                       ME->getMemberDecl()->getDeclName(),
                       ME->getTemplateArgs(), ME->getNumTemplateArgs(),
                       Arity);
      break;
    }
  
    case Expr::UnresolvedMemberExprClass: {
      const UnresolvedMemberExpr *ME = cast<UnresolvedMemberExpr>(E);
      mangleMemberExpr(ME->isImplicitAccess() ? nullptr : ME->getBase(),
                       ME->isArrow(), ME->getQualifier(), nullptr,
                       ME->getMemberName(),
                       ME->getTemplateArgs(), ME->getNumTemplateArgs(),
                       Arity);
      break;
    }
  
    case Expr::CXXDependentScopeMemberExprClass: {
      const CXXDependentScopeMemberExpr *ME
        = cast<CXXDependentScopeMemberExpr>(E);
      mangleMemberExpr(ME->isImplicitAccess() ? nullptr : ME->getBase(),
                       ME->isArrow(), ME->getQualifier(),
                       ME->getFirstQualifierFoundInScope(),
                       ME->getMember(),
                       ME->getTemplateArgs(), ME->getNumTemplateArgs(),
                       Arity);
      break;
    }
  
    case Expr::UnresolvedLookupExprClass: {
      const UnresolvedLookupExpr *ULE = cast<UnresolvedLookupExpr>(E);
      mangleUnresolvedName(ULE->getQualifier(), ULE->getName(),
                           ULE->getTemplateArgs(), ULE->getNumTemplateArgs(),
                           Arity);
      break;
    }
  
    case Expr::CXXUnresolvedConstructExprClass: {
      const CXXUnresolvedConstructExpr *CE = cast<CXXUnresolvedConstructExpr>(E);
      unsigned N = CE->getNumArgs();
  
      if (CE->isListInitialization()) {
        assert(N == 1 && "unexpected form for list initialization");
        auto *IL = cast<InitListExpr>(CE->getArg(0));
        Out << "tl";
        mangleType(CE->getType());
        mangleInitListElements(IL);
        Out << "E";
        return;
      }
  
      Out << "cv";
      mangleType(CE->getType());
      if (N != 1) Out << '_';
      for (unsigned I = 0; I != N; ++I) mangleExpression(CE->getArg(I));
      if (N != 1) Out << 'E';
      break;
    }
  
    case Expr::CXXConstructExprClass: {
      const auto *CE = cast<CXXConstructExpr>(E);
      if (!CE->isListInitialization() || CE->isStdInitListInitialization()) {
        assert(
            CE->getNumArgs() >= 1 &&
            (CE->getNumArgs() == 1 || isa<CXXDefaultArgExpr>(CE->getArg(1))) &&
            "implicit CXXConstructExpr must have one argument");
        return mangleExpression(cast<CXXConstructExpr>(E)->getArg(0));
      }
      Out << "il";
      for (auto *E : CE->arguments())
        mangleExpression(E);
      Out << "E";
      break;
    }
  
    case Expr::CXXTemporaryObjectExprClass: {
      const auto *CE = cast<CXXTemporaryObjectExpr>(E);
      unsigned N = CE->getNumArgs();
      bool List = CE->isListInitialization();
  
      if (List)
        Out << "tl";
      else
        Out << "cv";
      mangleType(CE->getType());
      if (!List && N != 1)
        Out << '_';
      if (CE->isStdInitListInitialization()) {
        // We implicitly created a std::initializer_list<T> for the first argument
        // of a constructor of type U in an expression of the form U{a, b, c}.
        // Strip all the semantic gunk off the initializer list.
        auto *SILE =
            cast<CXXStdInitializerListExpr>(CE->getArg(0)->IgnoreImplicit());
        auto *ILE = cast<InitListExpr>(SILE->getSubExpr()->IgnoreImplicit());
        mangleInitListElements(ILE);
      } else {
        for (auto *E : CE->arguments())
          mangleExpression(E);
      }
      if (List || N != 1)
        Out << 'E';
      break;
    }
  
    case Expr::CXXScalarValueInitExprClass:
      Out << "cv";
      mangleType(E->getType());
      Out << "_E";
      break;
  
    case Expr::CXXNoexceptExprClass:
      Out << "nx";
      mangleExpression(cast<CXXNoexceptExpr>(E)->getOperand());
      break;
  
    case Expr::UnaryExprOrTypeTraitExprClass: {
      const UnaryExprOrTypeTraitExpr *SAE = cast<UnaryExprOrTypeTraitExpr>(E);
  
      if (!SAE->isInstantiationDependent()) {
        // Itanium C++ ABI:
        //   If the operand of a sizeof or alignof operator is not
        //   instantiation-dependent it is encoded as an integer literal
        //   reflecting the result of the operator.
        //
        //   If the result of the operator is implicitly converted to a known
        //   integer type, that type is used for the literal; otherwise, the type
        //   of std::size_t or std::ptrdiff_t is used.
        QualType T = (ImplicitlyConvertedToType.isNull() ||
                      !ImplicitlyConvertedToType->isIntegerType())? SAE->getType()
                                                      : ImplicitlyConvertedToType;
        llvm::APSInt V = SAE->EvaluateKnownConstInt(Context.getASTContext());
        mangleIntegerLiteral(T, V);
        break;
      }
  
      switch(SAE->getKind()) {
      case UETT_SizeOf:
        Out << 's';
        break;
      case UETT_PreferredAlignOf:
      case UETT_AlignOf:
        Out << 'a';
        break;
      case UETT_VecStep: {
        DiagnosticsEngine &Diags = Context.getDiags();
        unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
                                       "cannot yet mangle vec_step expression");
        Diags.Report(DiagID);
        return;
      }
      case UETT_OpenMPRequiredSimdAlign: {
        DiagnosticsEngine &Diags = Context.getDiags();
        unsigned DiagID = Diags.getCustomDiagID(
            DiagnosticsEngine::Error,
            "cannot yet mangle __builtin_omp_required_simd_align expression");
        Diags.Report(DiagID);
        return;
      }
      }
      if (SAE->isArgumentType()) {
        Out << 't';
        mangleType(SAE->getArgumentType());
      } else {
        Out << 'z';
        mangleExpression(SAE->getArgumentExpr());
      }
      break;
    }
  
    case Expr::CXXThrowExprClass: {
      const CXXThrowExpr *TE = cast<CXXThrowExpr>(E);
      //  <expression> ::= tw <expression>  # throw expression
      //               ::= tr               # rethrow
      if (TE->getSubExpr()) {
        Out << "tw";
        mangleExpression(TE->getSubExpr());
      } else {
        Out << "tr";
      }
      break;
    }
  
    case Expr::CXXTypeidExprClass: {
      const CXXTypeidExpr *TIE = cast<CXXTypeidExpr>(E);
      //  <expression> ::= ti <type>        # typeid (type)
      //               ::= te <expression>  # typeid (expression)
      if (TIE->isTypeOperand()) {
        Out << "ti";
        mangleType(TIE->getTypeOperand(Context.getASTContext()));
      } else {
        Out << "te";
        mangleExpression(TIE->getExprOperand());
      }
      break;
    }
  
    case Expr::CXXDeleteExprClass: {
      const CXXDeleteExpr *DE = cast<CXXDeleteExpr>(E);
      //  <expression> ::= [gs] dl <expression>  # [::] delete expr
      //               ::= [gs] da <expression>  # [::] delete [] expr
      if (DE->isGlobalDelete()) Out << "gs";
      Out << (DE->isArrayForm() ? "da" : "dl");
      mangleExpression(DE->getArgument());
      break;
    }
  
    case Expr::UnaryOperatorClass: {
      const UnaryOperator *UO = cast<UnaryOperator>(E);
      mangleOperatorName(UnaryOperator::getOverloadedOperator(UO->getOpcode()),
                         /*Arity=*/1);
      mangleExpression(UO->getSubExpr());
      break;
    }
  
    case Expr::ArraySubscriptExprClass: {
      const ArraySubscriptExpr *AE = cast<ArraySubscriptExpr>(E);
  
      // Array subscript is treated as a syntactically weird form of
      // binary operator.
      Out << "ix";
      mangleExpression(AE->getLHS());
      mangleExpression(AE->getRHS());
      break;
    }
  
    case Expr::MatrixSubscriptExprClass: {
      const MatrixSubscriptExpr *ME = cast<MatrixSubscriptExpr>(E);
      Out << "ixix";
      mangleExpression(ME->getBase());
      mangleExpression(ME->getRowIdx());
      mangleExpression(ME->getColumnIdx());
      break;
    }
  
    case Expr::CompoundAssignOperatorClass: // fallthrough
    case Expr::BinaryOperatorClass: {
      const BinaryOperator *BO = cast<BinaryOperator>(E);
      if (BO->getOpcode() == BO_PtrMemD)
        Out << "ds";
      else
        mangleOperatorName(BinaryOperator::getOverloadedOperator(BO->getOpcode()),
                           /*Arity=*/2);
      mangleExpression(BO->getLHS());
      mangleExpression(BO->getRHS());
      break;
    }
  
    case Expr::CXXRewrittenBinaryOperatorClass: {
      // The mangled form represents the original syntax.
      CXXRewrittenBinaryOperator::DecomposedForm Decomposed =
          cast<CXXRewrittenBinaryOperator>(E)->getDecomposedForm();
      mangleOperatorName(BinaryOperator::getOverloadedOperator(Decomposed.Opcode),
                         /*Arity=*/2);
      mangleExpression(Decomposed.LHS);
      mangleExpression(Decomposed.RHS);
      break;
    }
  
    case Expr::ConditionalOperatorClass: {
      const ConditionalOperator *CO = cast<ConditionalOperator>(E);
      mangleOperatorName(OO_Conditional, /*Arity=*/3);
      mangleExpression(CO->getCond());
      mangleExpression(CO->getLHS(), Arity);
      mangleExpression(CO->getRHS(), Arity);
      break;
    }
  
    case Expr::ImplicitCastExprClass: {
      ImplicitlyConvertedToType = E->getType();
      E = cast<ImplicitCastExpr>(E)->getSubExpr();
      goto recurse;
    }
  
    case Expr::ObjCBridgedCastExprClass: {
      // Mangle ownership casts as a vendor extended operator __bridge,
      // __bridge_transfer, or __bridge_retain.
      StringRef Kind = cast<ObjCBridgedCastExpr>(E)->getBridgeKindName();
      Out << "v1U" << Kind.size() << Kind;
    }
    // Fall through to mangle the cast itself.
    LLVM_FALLTHROUGH;
  
    case Expr::CStyleCastExprClass:
      mangleCastExpression(E, "cv");
      break;
  
    case Expr::CXXFunctionalCastExprClass: {
      auto *Sub = cast<ExplicitCastExpr>(E)->getSubExpr()->IgnoreImplicit();
      // FIXME: Add isImplicit to CXXConstructExpr.
      if (auto *CCE = dyn_cast<CXXConstructExpr>(Sub))
        if (CCE->getParenOrBraceRange().isInvalid())
          Sub = CCE->getArg(0)->IgnoreImplicit();
      if (auto *StdInitList = dyn_cast<CXXStdInitializerListExpr>(Sub))
        Sub = StdInitList->getSubExpr()->IgnoreImplicit();
      if (auto *IL = dyn_cast<InitListExpr>(Sub)) {
        Out << "tl";
        mangleType(E->getType());
        mangleInitListElements(IL);
        Out << "E";
      } else {
        mangleCastExpression(E, "cv");
      }
      break;
    }
  
    case Expr::CXXStaticCastExprClass:
      mangleCastExpression(E, "sc");
      break;
    case Expr::CXXDynamicCastExprClass:
      mangleCastExpression(E, "dc");
      break;
    case Expr::CXXReinterpretCastExprClass:
      mangleCastExpression(E, "rc");
      break;
    case Expr::CXXConstCastExprClass:
      mangleCastExpression(E, "cc");
      break;
    case Expr::CXXAddrspaceCastExprClass:
      mangleCastExpression(E, "ac");
      break;
  
    case Expr::CXXOperatorCallExprClass: {
      const CXXOperatorCallExpr *CE = cast<CXXOperatorCallExpr>(E);
      unsigned NumArgs = CE->getNumArgs();
      // A CXXOperatorCallExpr for OO_Arrow models only semantics, not syntax
      // (the enclosing MemberExpr covers the syntactic portion).
      if (CE->getOperator() != OO_Arrow)
        mangleOperatorName(CE->getOperator(), /*Arity=*/NumArgs);
      // Mangle the arguments.
      for (unsigned i = 0; i != NumArgs; ++i)
        mangleExpression(CE->getArg(i));
      break;
    }
  
    case Expr::ParenExprClass:
      mangleExpression(cast<ParenExpr>(E)->getSubExpr(), Arity);
      break;
  
  
    case Expr::ConceptSpecializationExprClass: {
      //  <expr-primary> ::= L <mangled-name> E # external name
      Out << "L_Z";
      auto *CSE = cast<ConceptSpecializationExpr>(E);
      mangleTemplateName(CSE->getNamedConcept(),
                         CSE->getTemplateArguments().data(),
                         CSE->getTemplateArguments().size());
      Out << 'E';
      break;
    }
  
    case Expr::DeclRefExprClass:
      mangleDeclRefExpr(cast<DeclRefExpr>(E)->getDecl());
      break;
  
    case Expr::SubstNonTypeTemplateParmPackExprClass:
      // FIXME: not clear how to mangle this!
      // template <unsigned N...> class A {
      //   template <class U...> void foo(U (&x)[N]...);
      // };
      Out << "_SUBSTPACK_";
      break;
  
    case Expr::FunctionParmPackExprClass: {
      // FIXME: not clear how to mangle this!
      const FunctionParmPackExpr *FPPE = cast<FunctionParmPackExpr>(E);
      Out << "v110_SUBSTPACK";
      mangleDeclRefExpr(FPPE->getParameterPack());
      break;
    }
  
    case Expr::DependentScopeDeclRefExprClass: {
      const DependentScopeDeclRefExpr *DRE = cast<DependentScopeDeclRefExpr>(E);
      mangleUnresolvedName(DRE->getQualifier(), DRE->getDeclName(),
                           DRE->getTemplateArgs(), DRE->getNumTemplateArgs(),
                           Arity);
      break;
    }
  
    case Expr::CXXBindTemporaryExprClass:
      mangleExpression(cast<CXXBindTemporaryExpr>(E)->getSubExpr());
      break;
  
    case Expr::ExprWithCleanupsClass:
      mangleExpression(cast<ExprWithCleanups>(E)->getSubExpr(), Arity);
      break;
  
    case Expr::FloatingLiteralClass: {
      const FloatingLiteral *FL = cast<FloatingLiteral>(E);
      Out << 'L';
      mangleType(FL->getType());
      mangleFloat(FL->getValue());
      Out << 'E';
      break;
    }
  
    case Expr::CharacterLiteralClass:
      Out << 'L';
      mangleType(E->getType());
      Out << cast<CharacterLiteral>(E)->getValue();
      Out << 'E';
      break;
  
    // FIXME. __objc_yes/__objc_no are mangled same as true/false
    case Expr::ObjCBoolLiteralExprClass:
      Out << "Lb";
      Out << (cast<ObjCBoolLiteralExpr>(E)->getValue() ? '1' : '0');
      Out << 'E';
      break;
  
    case Expr::CXXBoolLiteralExprClass:
      Out << "Lb";
      Out << (cast<CXXBoolLiteralExpr>(E)->getValue() ? '1' : '0');
      Out << 'E';
      break;
  
    case Expr::IntegerLiteralClass: {
      llvm::APSInt Value(cast<IntegerLiteral>(E)->getValue());
      if (E->getType()->isSignedIntegerType())
        Value.setIsSigned(true);
      mangleIntegerLiteral(E->getType(), Value);
      break;
    }
  
    case Expr::ImaginaryLiteralClass: {
      const ImaginaryLiteral *IE = cast<ImaginaryLiteral>(E);
      // Mangle as if a complex literal.
      // Proposal from David Vandevoorde, 2010.06.30.
      Out << 'L';
      mangleType(E->getType());
      if (const FloatingLiteral *Imag =
            dyn_cast<FloatingLiteral>(IE->getSubExpr())) {
        // Mangle a floating-point zero of the appropriate type.
        mangleFloat(llvm::APFloat(Imag->getValue().getSemantics()));
        Out << '_';
        mangleFloat(Imag->getValue());
      } else {
        Out << "0_";
        llvm::APSInt Value(cast<IntegerLiteral>(IE->getSubExpr())->getValue());
        if (IE->getSubExpr()->getType()->isSignedIntegerType())
          Value.setIsSigned(true);
        mangleNumber(Value);
      }
      Out << 'E';
      break;
    }
  
    case Expr::StringLiteralClass: {
      // Revised proposal from David Vandervoorde, 2010.07.15.
      Out << 'L';
      assert(isa<ConstantArrayType>(E->getType()));
      mangleType(E->getType());
      Out << 'E';
      break;
    }
  
    case Expr::GNUNullExprClass:
      // Mangle as if an integer literal 0.
      Out << 'L';
      mangleType(E->getType());
      Out << "0E";
      break;
  
    case Expr::CXXNullPtrLiteralExprClass: {
      Out << "LDnE";
      break;
    }
  
    case Expr::PackExpansionExprClass:
      Out << "sp";
      mangleExpression(cast<PackExpansionExpr>(E)->getPattern());
      break;
  
    case Expr::SizeOfPackExprClass: {
      auto *SPE = cast<SizeOfPackExpr>(E);
      if (SPE->isPartiallySubstituted()) {
        Out << "sP";
        for (const auto &A : SPE->getPartialArguments())
          mangleTemplateArg(A);
        Out << "E";
        break;
      }
  
      Out << "sZ";
      const NamedDecl *Pack = SPE->getPack();
      if (const TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(Pack))
        mangleTemplateParameter(TTP->getDepth(), TTP->getIndex());
      else if (const NonTypeTemplateParmDecl *NTTP
                  = dyn_cast<NonTypeTemplateParmDecl>(Pack))
        mangleTemplateParameter(NTTP->getDepth(), NTTP->getIndex());
      else if (const TemplateTemplateParmDecl *TempTP
                                      = dyn_cast<TemplateTemplateParmDecl>(Pack))
        mangleTemplateParameter(TempTP->getDepth(), TempTP->getIndex());
      else
        mangleFunctionParam(cast<ParmVarDecl>(Pack));
      break;
    }
  
    case Expr::MaterializeTemporaryExprClass: {
      mangleExpression(cast<MaterializeTemporaryExpr>(E)->getSubExpr());
      break;
    }
  
    case Expr::CXXFoldExprClass: {
      auto *FE = cast<CXXFoldExpr>(E);
      if (FE->isLeftFold())
        Out << (FE->getInit() ? "fL" : "fl");
      else
        Out << (FE->getInit() ? "fR" : "fr");
  
      if (FE->getOperator() == BO_PtrMemD)
        Out << "ds";
      else
        mangleOperatorName(
            BinaryOperator::getOverloadedOperator(FE->getOperator()),
            /*Arity=*/2);
  
      if (FE->getLHS())
        mangleExpression(FE->getLHS());
      if (FE->getRHS())
        mangleExpression(FE->getRHS());
      break;
    }
  
    case Expr::CXXThisExprClass:
      Out << "fpT";
      break;
  
    case Expr::CoawaitExprClass:
      // FIXME: Propose a non-vendor mangling.
      Out << "v18co_await";
      mangleExpression(cast<CoawaitExpr>(E)->getOperand());
      break;
  
    case Expr::DependentCoawaitExprClass:
      // FIXME: Propose a non-vendor mangling.
      Out << "v18co_await";
      mangleExpression(cast<DependentCoawaitExpr>(E)->getOperand());
      break;
  
    case Expr::CoyieldExprClass:
      // FIXME: Propose a non-vendor mangling.
      Out << "v18co_yield";
      mangleExpression(cast<CoawaitExpr>(E)->getOperand());
      break;
    }
  }
  
  /// Mangle an expression which refers to a parameter variable.
  ///
  /// <expression>     ::= <function-param>
  /// <function-param> ::= fp <top-level CV-qualifiers> _      # L == 0, I == 0
  /// <function-param> ::= fp <top-level CV-qualifiers>
  ///                      <parameter-2 non-negative number> _ # L == 0, I > 0
  /// <function-param> ::= fL <L-1 non-negative number>
  ///                      p <top-level CV-qualifiers> _       # L > 0, I == 0
  /// <function-param> ::= fL <L-1 non-negative number>
  ///                      p <top-level CV-qualifiers>
  ///                      <I-1 non-negative number> _         # L > 0, I > 0
  ///
  /// L is the nesting depth of the parameter, defined as 1 if the
  /// parameter comes from the innermost function prototype scope
  /// enclosing the current context, 2 if from the next enclosing
  /// function prototype scope, and so on, with one special case: if
  /// we've processed the full parameter clause for the innermost
  /// function type, then L is one less.  This definition conveniently
  /// makes it irrelevant whether a function's result type was written
  /// trailing or leading, but is otherwise overly complicated; the
  /// numbering was first designed without considering references to
  /// parameter in locations other than return types, and then the
  /// mangling had to be generalized without changing the existing
  /// manglings.
  ///
  /// I is the zero-based index of the parameter within its parameter
  /// declaration clause.  Note that the original ABI document describes
  /// this using 1-based ordinals.
  void CXXNameMangler::mangleFunctionParam(const ParmVarDecl *parm) {
    unsigned parmDepth = parm->getFunctionScopeDepth();
    unsigned parmIndex = parm->getFunctionScopeIndex();
  
    // Compute 'L'.
    // parmDepth does not include the declaring function prototype.
    // FunctionTypeDepth does account for that.
    assert(parmDepth < FunctionTypeDepth.getDepth());
    unsigned nestingDepth = FunctionTypeDepth.getDepth() - parmDepth;
    if (FunctionTypeDepth.isInResultType())
      nestingDepth--;
  
    if (nestingDepth == 0) {
      Out << "fp";
    } else {
      Out << "fL" << (nestingDepth - 1) << 'p';
    }
  
    // Top-level qualifiers.  We don't have to worry about arrays here,
    // because parameters declared as arrays should already have been
    // transformed to have pointer type. FIXME: apparently these don't
    // get mangled if used as an rvalue of a known non-class type?
    assert(!parm->getType()->isArrayType()
           && "parameter's type is still an array type?");
  
    if (const DependentAddressSpaceType *DAST =
        dyn_cast<DependentAddressSpaceType>(parm->getType())) {
      mangleQualifiers(DAST->getPointeeType().getQualifiers(), DAST);
    } else {
      mangleQualifiers(parm->getType().getQualifiers());
    }
  
    // Parameter index.
    if (parmIndex != 0) {
      Out << (parmIndex - 1);
    }
    Out << '_';
  }
  
  void CXXNameMangler::mangleCXXCtorType(CXXCtorType T,
                                         const CXXRecordDecl *InheritedFrom) {
    // <ctor-dtor-name> ::= C1  # complete object constructor
    //                  ::= C2  # base object constructor
    //                  ::= CI1 <type> # complete inheriting constructor
    //                  ::= CI2 <type> # base inheriting constructor
    //
    // In addition, C5 is a comdat name with C1 and C2 in it.
    Out << 'C';
    if (InheritedFrom)
      Out << 'I';
    switch (T) {
    case Ctor_Complete:
      Out << '1';
      break;
    case Ctor_Base:
      Out << '2';
      break;
    case Ctor_Comdat:
      Out << '5';
      break;
    case Ctor_DefaultClosure:
    case Ctor_CopyingClosure:
      llvm_unreachable("closure constructors don't exist for the Itanium ABI!");
    }
    if (InheritedFrom)
      mangleName(InheritedFrom);
  }
  
  void CXXNameMangler::mangleCXXDtorType(CXXDtorType T) {
    // <ctor-dtor-name> ::= D0  # deleting destructor
    //                  ::= D1  # complete object destructor
    //                  ::= D2  # base object destructor
    //
    // In addition, D5 is a comdat name with D1, D2 and, if virtual, D0 in it.
    switch (T) {
    case Dtor_Deleting:
      Out << "D0";
      break;
    case Dtor_Complete:
      Out << "D1";
      break;
    case Dtor_Base:
      Out << "D2";
      break;
    case Dtor_Comdat:
      Out << "D5";
      break;
    }
  }
  
  void CXXNameMangler::mangleTemplateArgs(const TemplateArgumentLoc *TemplateArgs,
                                          unsigned NumTemplateArgs) {
    // <template-args> ::= I <template-arg>+ E
    Out << 'I';
    for (unsigned i = 0; i != NumTemplateArgs; ++i)
      mangleTemplateArg(TemplateArgs[i].getArgument());
    Out << 'E';
  }
  
  void CXXNameMangler::mangleTemplateArgs(const TemplateArgumentList &AL) {
    // <template-args> ::= I <template-arg>+ E
    Out << 'I';
    for (unsigned i = 0, e = AL.size(); i != e; ++i)
      mangleTemplateArg(AL[i]);
    Out << 'E';
  }
  
  void CXXNameMangler::mangleTemplateArgs(const TemplateArgument *TemplateArgs,
                                          unsigned NumTemplateArgs) {
    // <template-args> ::= I <template-arg>+ E
    Out << 'I';
    for (unsigned i = 0; i != NumTemplateArgs; ++i)
      mangleTemplateArg(TemplateArgs[i]);
    Out << 'E';
  }
  
  void CXXNameMangler::mangleTemplateArg(TemplateArgument A) {
    // <template-arg> ::= <type>              # type or template
    //                ::= X <expression> E    # expression
    //                ::= <expr-primary>      # simple expressions
    //                ::= J <template-arg>* E # argument pack
    if (!A.isInstantiationDependent() || A.isDependent())
      A = Context.getASTContext().getCanonicalTemplateArgument(A);
  
    switch (A.getKind()) {
    case TemplateArgument::Null:
      llvm_unreachable("Cannot mangle NULL template argument");
  
    case TemplateArgument::Type:
      mangleType(A.getAsType());
      break;
    case TemplateArgument::Template:
      // This is mangled as <type>.
      mangleType(A.getAsTemplate());
      break;
    case TemplateArgument::TemplateExpansion:
      // <type>  ::= Dp <type>          # pack expansion (C++0x)
      Out << "Dp";
      mangleType(A.getAsTemplateOrTemplatePattern());
      break;
    case TemplateArgument::Expression: {
      // It's possible to end up with a DeclRefExpr here in certain
      // dependent cases, in which case we should mangle as a
      // declaration.
      const Expr *E = A.getAsExpr()->IgnoreParenImpCasts();
      if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
        const ValueDecl *D = DRE->getDecl();
        if (isa<VarDecl>(D) || isa<FunctionDecl>(D)) {
          Out << 'L';
          mangle(D);
          Out << 'E';
          break;
        }
      }
  
      Out << 'X';
      mangleExpression(E);
      Out << 'E';
      break;
    }
    case TemplateArgument::Integral:
      mangleIntegerLiteral(A.getIntegralType(), A.getAsIntegral());
      break;
    case TemplateArgument::Declaration: {
      //  <expr-primary> ::= L <mangled-name> E # external name
      // Clang produces AST's where pointer-to-member-function expressions
      // and pointer-to-function expressions are represented as a declaration not
      // an expression. We compensate for it here to produce the correct mangling.
      ValueDecl *D = A.getAsDecl();
      bool compensateMangling = !A.getParamTypeForDecl()->isReferenceType();
      if (compensateMangling) {
        Out << 'X';
        mangleOperatorName(OO_Amp, 1);
      }
  
      Out << 'L';
      // References to external entities use the mangled name; if the name would
      // not normally be mangled then mangle it as unqualified.
      mangle(D);
      Out << 'E';
  
      if (compensateMangling)
        Out << 'E';
  
      break;
    }
    case TemplateArgument::NullPtr: {
      //  <expr-primary> ::= L <type> 0 E
      Out << 'L';
      mangleType(A.getNullPtrType());
      Out << "0E";
      break;
    }
    case TemplateArgument::Pack: {
      //  <template-arg> ::= J <template-arg>* E
      Out << 'J';
      for (const auto &P : A.pack_elements())
        mangleTemplateArg(P);
      Out << 'E';
    }
    }
  }
  
  void CXXNameMangler::mangleTemplateParameter(unsigned Depth, unsigned Index) {
    // <template-param> ::= T_    # first template parameter
    //                  ::= T <parameter-2 non-negative number> _
    //                  ::= TL <L-1 non-negative number> __
    //                  ::= TL <L-1 non-negative number> _
    //                         <parameter-2 non-negative number> _
    //
    // The latter two manglings are from a proposal here:
    // https://github.com/itanium-cxx-abi/cxx-abi/issues/31#issuecomment-528122117
    Out << 'T';
    if (Depth != 0)
      Out << 'L' << (Depth - 1) << '_';
    if (Index != 0)
      Out << (Index - 1);
    Out << '_';
  }
  
  void CXXNameMangler::mangleSeqID(unsigned SeqID) {
    if (SeqID == 1)
      Out << '0';
    else if (SeqID > 1) {
      SeqID--;
  
      // <seq-id> is encoded in base-36, using digits and upper case letters.
      char Buffer[7]; // log(2**32) / log(36) ~= 7
      MutableArrayRef<char> BufferRef(Buffer);
      MutableArrayRef<char>::reverse_iterator I = BufferRef.rbegin();
  
      for (; SeqID != 0; SeqID /= 36) {
        unsigned C = SeqID % 36;
        *I++ = (C < 10 ? '0' + C : 'A' + C - 10);
      }
  
      Out.write(I.base(), I - BufferRef.rbegin());
    }
    Out << '_';
  }
  
  void CXXNameMangler::mangleExistingSubstitution(TemplateName tname) {
    bool result = mangleSubstitution(tname);
    assert(result && "no existing substitution for template name");
    (void) result;
  }
  
  // <substitution> ::= S <seq-id> _
  //                ::= S_
  bool CXXNameMangler::mangleSubstitution(const NamedDecl *ND) {
    // Try one of the standard substitutions first.
    if (mangleStandardSubstitution(ND))
      return true;
  
    ND = cast<NamedDecl>(ND->getCanonicalDecl());
    return mangleSubstitution(reinterpret_cast<uintptr_t>(ND));
  }
  
  /// Determine whether the given type has any qualifiers that are relevant for
  /// substitutions.
  static bool hasMangledSubstitutionQualifiers(QualType T) {
    Qualifiers Qs = T.getQualifiers();
    return Qs.getCVRQualifiers() || Qs.hasAddressSpace() || Qs.hasUnaligned();
  }
  
  bool CXXNameMangler::mangleSubstitution(QualType T) {
    if (!hasMangledSubstitutionQualifiers(T)) {
      if (const RecordType *RT = T->getAs<RecordType>())
        return mangleSubstitution(RT->getDecl());
    }
  
    uintptr_t TypePtr = reinterpret_cast<uintptr_t>(T.getAsOpaquePtr());
  
    return mangleSubstitution(TypePtr);
  }
  
  bool CXXNameMangler::mangleSubstitution(TemplateName Template) {
    if (TemplateDecl *TD = Template.getAsTemplateDecl())
      return mangleSubstitution(TD);
  
    Template = Context.getASTContext().getCanonicalTemplateName(Template);
    return mangleSubstitution(
                        reinterpret_cast<uintptr_t>(Template.getAsVoidPointer()));
  }
  
  bool CXXNameMangler::mangleSubstitution(uintptr_t Ptr) {
    llvm::DenseMap<uintptr_t, unsigned>::iterator I = Substitutions.find(Ptr);
    if (I == Substitutions.end())
      return false;
  
    unsigned SeqID = I->second;
    Out << 'S';
    mangleSeqID(SeqID);
  
    return true;
  }
  
  static bool isCharType(QualType T) {
    if (T.isNull())
      return false;
  
    return T->isSpecificBuiltinType(BuiltinType::Char_S) ||
      T->isSpecificBuiltinType(BuiltinType::Char_U);
  }
  
  /// Returns whether a given type is a template specialization of a given name
  /// with a single argument of type char.
  static bool isCharSpecialization(QualType T, const char *Name) {
    if (T.isNull())
      return false;
  
    const RecordType *RT = T->getAs<RecordType>();
    if (!RT)
      return false;
  
    const ClassTemplateSpecializationDecl *SD =
      dyn_cast<ClassTemplateSpecializationDecl>(RT->getDecl());
    if (!SD)
      return false;
  
    if (!isStdNamespace(getEffectiveDeclContext(SD)))
      return false;
  
    const TemplateArgumentList &TemplateArgs = SD->getTemplateArgs();
    if (TemplateArgs.size() != 1)
      return false;
  
    if (!isCharType(TemplateArgs[0].getAsType()))
      return false;
  
    return SD->getIdentifier()->getName() == Name;
  }
  
  template <std::size_t StrLen>
  static bool isStreamCharSpecialization(const ClassTemplateSpecializationDecl*SD,
                                         const char (&Str)[StrLen]) {
    if (!SD->getIdentifier()->isStr(Str))
      return false;
  
    const TemplateArgumentList &TemplateArgs = SD->getTemplateArgs();
    if (TemplateArgs.size() != 2)
      return false;
  
    if (!isCharType(TemplateArgs[0].getAsType()))
      return false;
  
    if (!isCharSpecialization(TemplateArgs[1].getAsType(), "char_traits"))
      return false;
  
    return true;
  }
  
  bool CXXNameMangler::mangleStandardSubstitution(const NamedDecl *ND) {
    // <substitution> ::= St # ::std::
    if (const NamespaceDecl *NS = dyn_cast<NamespaceDecl>(ND)) {
      if (isStd(NS)) {
        Out << "St";
        return true;
      }
    }
  
    if (const ClassTemplateDecl *TD = dyn_cast<ClassTemplateDecl>(ND)) {
      if (!isStdNamespace(getEffectiveDeclContext(TD)))
        return false;
  
      // <substitution> ::= Sa # ::std::allocator
      if (TD->getIdentifier()->isStr("allocator")) {
        Out << "Sa";
        return true;
      }
  
      // <<substitution> ::= Sb # ::std::basic_string
      if (TD->getIdentifier()->isStr("basic_string")) {
        Out << "Sb";
        return true;
      }
    }
  
    if (const ClassTemplateSpecializationDecl *SD =
          dyn_cast<ClassTemplateSpecializationDecl>(ND)) {
      if (!isStdNamespace(getEffectiveDeclContext(SD)))
        return false;
  
      //    <substitution> ::= Ss # ::std::basic_string<char,
      //                            ::std::char_traits<char>,
      //                            ::std::allocator<char> >
      if (SD->getIdentifier()->isStr("basic_string")) {
        const TemplateArgumentList &TemplateArgs = SD->getTemplateArgs();
  
        if (TemplateArgs.size() != 3)
          return false;
  
        if (!isCharType(TemplateArgs[0].getAsType()))
          return false;
  
        if (!isCharSpecialization(TemplateArgs[1].getAsType(), "char_traits"))
          return false;
  
        if (!isCharSpecialization(TemplateArgs[2].getAsType(), "allocator"))
          return false;
  
        Out << "Ss";
        return true;
      }
  
      //    <substitution> ::= Si # ::std::basic_istream<char,
      //                            ::std::char_traits<char> >
      if (isStreamCharSpecialization(SD, "basic_istream")) {
        Out << "Si";
        return true;
      }
  
      //    <substitution> ::= So # ::std::basic_ostream<char,
      //                            ::std::char_traits<char> >
      if (isStreamCharSpecialization(SD, "basic_ostream")) {
        Out << "So";
        return true;
      }
  
      //    <substitution> ::= Sd # ::std::basic_iostream<char,
      //                            ::std::char_traits<char> >
      if (isStreamCharSpecialization(SD, "basic_iostream")) {
        Out << "Sd";
        return true;
      }
    }
    return false;
  }
  
  void CXXNameMangler::addSubstitution(QualType T) {
    if (!hasMangledSubstitutionQualifiers(T)) {
      if (const RecordType *RT = T->getAs<RecordType>()) {
        addSubstitution(RT->getDecl());
        return;
      }
    }
  
    uintptr_t TypePtr = reinterpret_cast<uintptr_t>(T.getAsOpaquePtr());
    addSubstitution(TypePtr);
  }
  
  void CXXNameMangler::addSubstitution(TemplateName Template) {
    if (TemplateDecl *TD = Template.getAsTemplateDecl())
      return addSubstitution(TD);
  
    Template = Context.getASTContext().getCanonicalTemplateName(Template);
    addSubstitution(reinterpret_cast<uintptr_t>(Template.getAsVoidPointer()));
  }
  
  void CXXNameMangler::addSubstitution(uintptr_t Ptr) {
    assert(!Substitutions.count(Ptr) && "Substitution already exists!");
    Substitutions[Ptr] = SeqID++;
  }
  
  void CXXNameMangler::extendSubstitutions(CXXNameMangler* Other) {
    assert(Other->SeqID >= SeqID && "Must be superset of substitutions!");
    if (Other->SeqID > SeqID) {
      Substitutions.swap(Other->Substitutions);
      SeqID = Other->SeqID;
    }
  }
  
  CXXNameMangler::AbiTagList
  CXXNameMangler::makeFunctionReturnTypeTags(const FunctionDecl *FD) {
    // When derived abi tags are disabled there is no need to make any list.
    if (DisableDerivedAbiTags)
      return AbiTagList();
  
    llvm::raw_null_ostream NullOutStream;
    CXXNameMangler TrackReturnTypeTags(*this, NullOutStream);
    TrackReturnTypeTags.disableDerivedAbiTags();
  
    const FunctionProtoType *Proto =
        cast<FunctionProtoType>(FD->getType()->getAs<FunctionType>());
    FunctionTypeDepthState saved = TrackReturnTypeTags.FunctionTypeDepth.push();
    TrackReturnTypeTags.FunctionTypeDepth.enterResultType();
    TrackReturnTypeTags.mangleType(Proto->getReturnType());
    TrackReturnTypeTags.FunctionTypeDepth.leaveResultType();
    TrackReturnTypeTags.FunctionTypeDepth.pop(saved);
  
    return TrackReturnTypeTags.AbiTagsRoot.getSortedUniqueUsedAbiTags();
  }
  
  CXXNameMangler::AbiTagList
  CXXNameMangler::makeVariableTypeTags(const VarDecl *VD) {
    // When derived abi tags are disabled there is no need to make any list.
    if (DisableDerivedAbiTags)
      return AbiTagList();
  
    llvm::raw_null_ostream NullOutStream;
    CXXNameMangler TrackVariableType(*this, NullOutStream);
    TrackVariableType.disableDerivedAbiTags();
  
    TrackVariableType.mangleType(VD->getType());
  
    return TrackVariableType.AbiTagsRoot.getSortedUniqueUsedAbiTags();
  }
  
  bool CXXNameMangler::shouldHaveAbiTags(ItaniumMangleContextImpl &C,
                                         const VarDecl *VD) {
    llvm::raw_null_ostream NullOutStream;
    CXXNameMangler TrackAbiTags(C, NullOutStream, nullptr, true);
    TrackAbiTags.mangle(VD);
    return TrackAbiTags.AbiTagsRoot.getUsedAbiTags().size();
  }
  
  //
  
  /// Mangles the name of the declaration D and emits that name to the given
  /// output stream.
  ///
  /// If the declaration D requires a mangled name, this routine will emit that
  /// mangled name to \p os and return true. Otherwise, \p os will be unchanged
  /// and this routine will return false. In this case, the caller should just
  /// emit the identifier of the declaration (\c D->getIdentifier()) as its
  /// name.
  void ItaniumMangleContextImpl::mangleCXXName(GlobalDecl GD,
                                               raw_ostream &Out) {
    const NamedDecl *D = cast<NamedDecl>(GD.getDecl());
    assert((isa<FunctionDecl>(D) || isa<VarDecl>(D)) &&
            "Invalid mangleName() call, argument is not a variable or function!");
  
    PrettyStackTraceDecl CrashInfo(D, SourceLocation(),
                                   getASTContext().getSourceManager(),
                                   "Mangling declaration");
  
    if (auto *CD = dyn_cast<CXXConstructorDecl>(D)) {
      auto Type = GD.getCtorType();
      CXXNameMangler Mangler(*this, Out, CD, Type);
      return Mangler.mangle(GlobalDecl(CD, Type));
    }
  
    if (auto *DD = dyn_cast<CXXDestructorDecl>(D)) {
      auto Type = GD.getDtorType();
      CXXNameMangler Mangler(*this, Out, DD, Type);
      return Mangler.mangle(GlobalDecl(DD, Type));
    }
  
    CXXNameMangler Mangler(*this, Out, D);
    Mangler.mangle(GD);
  }
  
  void ItaniumMangleContextImpl::mangleCXXCtorComdat(const CXXConstructorDecl *D,
                                                     raw_ostream &Out) {
    CXXNameMangler Mangler(*this, Out, D, Ctor_Comdat);
    Mangler.mangle(GlobalDecl(D, Ctor_Comdat));
  }
  
  void ItaniumMangleContextImpl::mangleCXXDtorComdat(const CXXDestructorDecl *D,
                                                     raw_ostream &Out) {
    CXXNameMangler Mangler(*this, Out, D, Dtor_Comdat);
    Mangler.mangle(GlobalDecl(D, Dtor_Comdat));
  }
  
  void ItaniumMangleContextImpl::mangleThunk(const CXXMethodDecl *MD,
                                             const ThunkInfo &Thunk,
                                             raw_ostream &Out) {
    //  <special-name> ::= T <call-offset> <base encoding>
    //                      # base is the nominal target function of thunk
    //  <special-name> ::= Tc <call-offset> <call-offset> <base encoding>
    //                      # base is the nominal target function of thunk
    //                      # first call-offset is 'this' adjustment
    //                      # second call-offset is result adjustment
  
    assert(!isa<CXXDestructorDecl>(MD) &&
           "Use mangleCXXDtor for destructor decls!");
    CXXNameMangler Mangler(*this, Out);
    Mangler.getStream() << "_ZT";
    if (!Thunk.Return.isEmpty())
      Mangler.getStream() << 'c';
  
    // Mangle the 'this' pointer adjustment.
    Mangler.mangleCallOffset(Thunk.This.NonVirtual,
                             Thunk.This.Virtual.Itanium.VCallOffsetOffset);
  
    // Mangle the return pointer adjustment if there is one.
    if (!Thunk.Return.isEmpty())
      Mangler.mangleCallOffset(Thunk.Return.NonVirtual,
                               Thunk.Return.Virtual.Itanium.VBaseOffsetOffset);
  
    Mangler.mangleFunctionEncoding(MD);
  }
  
  void ItaniumMangleContextImpl::mangleCXXDtorThunk(
      const CXXDestructorDecl *DD, CXXDtorType Type,
      const ThisAdjustment &ThisAdjustment, raw_ostream &Out) {
    //  <special-name> ::= T <call-offset> <base encoding>
    //                      # base is the nominal target function of thunk
    CXXNameMangler Mangler(*this, Out, DD, Type);
    Mangler.getStream() << "_ZT";
  
    // Mangle the 'this' pointer adjustment.
    Mangler.mangleCallOffset(ThisAdjustment.NonVirtual,
                             ThisAdjustment.Virtual.Itanium.VCallOffsetOffset);
  
    Mangler.mangleFunctionEncoding(GlobalDecl(DD, Type));
  }
  
  /// Returns the mangled name for a guard variable for the passed in VarDecl.
  void ItaniumMangleContextImpl::mangleStaticGuardVariable(const VarDecl *D,
                                                           raw_ostream &Out) {
    //  <special-name> ::= GV <object name>       # Guard variable for one-time
    //                                            # initialization
    CXXNameMangler Mangler(*this, Out);
    // GCC 5.3.0 doesn't emit derived ABI tags for local names but that seems to
    // be a bug that is fixed in trunk.
    Mangler.getStream() << "_ZGV";
    Mangler.mangleName(D);
  }
  
  void ItaniumMangleContextImpl::mangleDynamicInitializer(const VarDecl *MD,
                                                          raw_ostream &Out) {
    // These symbols are internal in the Itanium ABI, so the names don't matter.
    // Clang has traditionally used this symbol and allowed LLVM to adjust it to
    // avoid duplicate symbols.
    Out << "__cxx_global_var_init";
  }
  
  void ItaniumMangleContextImpl::mangleDynamicAtExitDestructor(const VarDecl *D,
                                                               raw_ostream &Out) {
    // Prefix the mangling of D with __dtor_.
    CXXNameMangler Mangler(*this, Out);
    Mangler.getStream() << "__dtor_";
    if (shouldMangleDeclName(D))
      Mangler.mangle(D);
    else
      Mangler.getStream() << D->getName();
  }
  
  void ItaniumMangleContextImpl::mangleDynamicStermFinalizer(const VarDecl *D,
                                                             raw_ostream &Out) {
    // Clang generates these internal-linkage functions as part of its
    // implementation of the XL ABI.
    CXXNameMangler Mangler(*this, Out);
    Mangler.getStream() << "__finalize_";
    if (shouldMangleDeclName(D))
      Mangler.mangle(D);
    else
      Mangler.getStream() << D->getName();
  }
  
  void ItaniumMangleContextImpl::mangleSEHFilterExpression(
      const NamedDecl *EnclosingDecl, raw_ostream &Out) {
    CXXNameMangler Mangler(*this, Out);
    Mangler.getStream() << "__filt_";
    if (shouldMangleDeclName(EnclosingDecl))
      Mangler.mangle(EnclosingDecl);
    else
      Mangler.getStream() << EnclosingDecl->getName();
  }
  
  void ItaniumMangleContextImpl::mangleSEHFinallyBlock(
      const NamedDecl *EnclosingDecl, raw_ostream &Out) {
    CXXNameMangler Mangler(*this, Out);
    Mangler.getStream() << "__fin_";
    if (shouldMangleDeclName(EnclosingDecl))
      Mangler.mangle(EnclosingDecl);
    else
      Mangler.getStream() << EnclosingDecl->getName();
  }
  
  void ItaniumMangleContextImpl::mangleItaniumThreadLocalInit(const VarDecl *D,
                                                              raw_ostream &Out) {
    //  <special-name> ::= TH <object name>
    CXXNameMangler Mangler(*this, Out);
    Mangler.getStream() << "_ZTH";
    Mangler.mangleName(D);
  }
  
  void
  ItaniumMangleContextImpl::mangleItaniumThreadLocalWrapper(const VarDecl *D,
                                                            raw_ostream &Out) {
    //  <special-name> ::= TW <object name>
    CXXNameMangler Mangler(*this, Out);
    Mangler.getStream() << "_ZTW";
    Mangler.mangleName(D);
  }
  
  void ItaniumMangleContextImpl::mangleReferenceTemporary(const VarDecl *D,
                                                          unsigned ManglingNumber,
                                                          raw_ostream &Out) {
    // We match the GCC mangling here.
    //  <special-name> ::= GR <object name>
    CXXNameMangler Mangler(*this, Out);
    Mangler.getStream() << "_ZGR";
    Mangler.mangleName(D);
    assert(ManglingNumber > 0 && "Reference temporary mangling number is zero!");
    Mangler.mangleSeqID(ManglingNumber - 1);
  }
  
  void ItaniumMangleContextImpl::mangleCXXVTable(const CXXRecordDecl *RD,
                                                 raw_ostream &Out) {
    // <special-name> ::= TV <type>  # virtual table
    CXXNameMangler Mangler(*this, Out);
    Mangler.getStream() << "_ZTV";
    Mangler.mangleNameOrStandardSubstitution(RD);
  }
  
  void ItaniumMangleContextImpl::mangleCXXVTT(const CXXRecordDecl *RD,
                                              raw_ostream &Out) {
    // <special-name> ::= TT <type>  # VTT structure
    CXXNameMangler Mangler(*this, Out);
    Mangler.getStream() << "_ZTT";
    Mangler.mangleNameOrStandardSubstitution(RD);
  }
  
  void ItaniumMangleContextImpl::mangleCXXCtorVTable(const CXXRecordDecl *RD,
                                                     int64_t Offset,
                                                     const CXXRecordDecl *Type,
                                                     raw_ostream &Out) {
    // <special-name> ::= TC <type> <offset number> _ <base type>
    CXXNameMangler Mangler(*this, Out);
    Mangler.getStream() << "_ZTC";
    Mangler.mangleNameOrStandardSubstitution(RD);
    Mangler.getStream() << Offset;
    Mangler.getStream() << '_';
    Mangler.mangleNameOrStandardSubstitution(Type);
  }
  
  void ItaniumMangleContextImpl::mangleCXXRTTI(QualType Ty, raw_ostream &Out) {
    // <special-name> ::= TI <type>  # typeinfo structure
    assert(!Ty.hasQualifiers() && "RTTI info cannot have top-level qualifiers");
    CXXNameMangler Mangler(*this, Out);
    Mangler.getStream() << "_ZTI";
    Mangler.mangleType(Ty);
  }
  
  void ItaniumMangleContextImpl::mangleCXXRTTIName(QualType Ty,
                                                   raw_ostream &Out) {
    // <special-name> ::= TS <type>  # typeinfo name (null terminated byte string)
    CXXNameMangler Mangler(*this, Out);
    Mangler.getStream() << "_ZTS";
    Mangler.mangleType(Ty);
  }
  
  void ItaniumMangleContextImpl::mangleTypeName(QualType Ty, raw_ostream &Out) {
    mangleCXXRTTIName(Ty, Out);
  }
  
  void ItaniumMangleContextImpl::mangleStringLiteral(const StringLiteral *, raw_ostream &) {
    llvm_unreachable("Can't mangle string literals");
  }
  
  void ItaniumMangleContextImpl::mangleLambdaSig(const CXXRecordDecl *Lambda,
                                                 raw_ostream &Out) {
    CXXNameMangler Mangler(*this, Out);
    Mangler.mangleLambdaSig(Lambda);
  }
  
  ItaniumMangleContext *
  ItaniumMangleContext::create(ASTContext &Context, DiagnosticsEngine &Diags) {
    return new ItaniumMangleContextImpl(Context, Diags);
  }
  